Synology DS1019+ v9 User's Guide PDF

1

User Guide for

Synology High Availability (SHA)

Based on DSM 7.0 and Synology High Availability 2.1.0

Table of Contents

Chapter 1: Introduction 01

Chapter 2: Required Environment 02

2.1 Supported models (as of January 2022)

2.2 System requirements

2.3 Limitations

Chapter 3: Set Up and Configure an SHA Cluster 07

3.1 Connect the hosts

3.2 Create a cluster

3.3 Tests and simulations

3.4 Set up storage for SHA

3.5 Monitored services

3.6 Quorum server

3.7 UPS

3.8 Power schedule

3.9 System notifications

Chapter 4: Navigate the SHA User Interface 28

4.1 Cluster

4.2 Host

4.3 Network

4.4 Service

4.5 Storage

4.6 Log

4.7 Split-brain

Chapter 5: Maintain your High-availability Cluster 37

5.1 Software updates

5.2 Drive firmware update

5.3 Network management

5.4 Storage capacity expansion

5.5 Memory expansion

5.6 M.2 SSD installation

5.7 Network interface card installation

5.8 Data migration

Learn more 51

Related articles

Software specs

Other resources

Date of publication: March 8, 2022

01

Chapter 1: Introduction

High Availability solutions are in high demand for anyone involved in the deployment of

important services such as databases, a company file server, virtualized storage, and more.

All of these services have extremely low tolerance and cannot afford to be interrupted in the

event of unexpected disasters or events.

Because of its high cost and complicated setup, high availability is typically portrayed as an

enterprise-only solution. However, Synology High Availability (SHA) is available on the

majority of plus-series and all FS/XS-series devices, making it a cost-effective solution for

protecting critical services. When a disaster strikes, SHA helps to reduce the impact on the

effort needed to resolve any system or hardware issues, while also allowing businesses to

avoid downtime for mission-critical applications and minimize lost revenue.

To achieve high availability, SHA utilizes two Synology NAS that function as either the active

or passive server to form a high-availability cluster. These servers are connected by a

Heartbeat connection, which is a dedicated, private network connection that facilitates data

synchronization and replication between the two devices. If the active server malfunctions or

a service is abnormal, services will automatically failover to the passive server for it to take

over services to minimize any downtime. With this in mind, users can rest assured that their

services are constantly maintained, even in the event of sudden disaster.

Those who wish to make full use of the support provided by Synology High Availability will

benefit from the information in this User Guide.

For information regarding SHA design and architecture, common scenarios, best practices, and

performance metrics, please refer to the SHA White Paper.

Chapter 1: Introduction

02

Chapter 2: Required Environment

2.1 Supported models (as of January 2022)

Please refer to the Applied Models section on this page for the latest information on SHA and

its supported devices.

Series Supported models

FS series FS6400, FS3600, FS3400, FS3017, FS2500, FS2017, FS1018

SA series SA3600, SA3400

22 series DS3622xs+, DS2422+

21 series RS4021xs+, RS3621xs+, RS3621RPxs, RS2821RP+, RS2421RP+, RS2421+, RS1221RP+, RS1221+, DS1821+, DS1621xs+, DS1621+

20 series RS820RP+, RS820+, DS1520+, DS920+, DS720+, DS620slim, DS420+, DS220+

19 series RS1619xs+, RS1219+, DS2419+II, DS2419+, DS1819+, DS1019+

18 series RS3618xs, RS2818RP+, RS2418RP+, RS2418+, RS818RP+, RS818+, DS3018xs, DS1618+, DS918+, DS718+

17 series RS18017xs+, RS4017xs+, RS3617xs+, RS3617RPxs, RS3617xs, DS3617xsII, DS3617xs, DS1817+, DS1817, DS1517+, DS1517

16 series RS18016xs+, RS2416RP+, RS2416+, DS916+, DS716+II, DS716+

15 series RS815RP+, RS815+, DS3615xs, DS2415+, DS2015xs, DS1815+, DS1515+, DS1515, DS715, DS415+

14 series RS3614xs+, RS3614RPxs, RS3614xs, RS2414RP+, RS2414+, RS814RP+, RS814+

13 series RS10613xs+, RS3413xs+, DS2413+, DS1813+, DS1513+, DS713+

12 series RS3412RPxs, RS3412xs, RS2212RP+, RS2212+, RS812RP+, RS812+, DS3612xs, DS1812+, DS1512+, DS412+

Chapter 2: Required Environment

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Chapter 1: Introduction

2.2 System requirements

In Synology High Availability (SHA), the active server and the passive server are referred to as

"hosts".

Models and versions

To create an SHA cluster, two Synology NAS (hosts) with support for SHA are required to act

as the active and passive servers.

We recommend that the models of the two hosts are identical, but you can also use two

hosts that are similar models to create a Hybrid High Availability cluster. For more

information, refer to this article.

Both hosts need to have the same DSM and Synology High Availability package versions

installed. We recommend you to install the latest versions.

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Chapter 1: Introduction

Volumes and disks

We recommend that the drive capacity of both hosts be identical.

The active and passive servers must have the same number of drives. Additionally, the

drives must be placed in the exact same slots on each device. Refer to the image below for

example:

The illustration above is for reference only. The number and size of disks in your environment may differ.

The hosts must not contain any SHR-formatted volumes. Go to Storage Manager > Volume

to make sure that no SHR volumes exist. If there are SHR volumes, you must remove them

before setting up a cluster. For information on how to change your RAID type, refer to this article.

To create an SSD cache on a SHA cluster, the memory capacity on each host must be

identical.

Network environment

Network settings

Make sure that your network settings meet the following requirements; otherwise, you may

experience connection errors after performing a failover.

Both hosts must be assigned static IP addresses for the Cluster connection.

Both hosts must connect to the same network via the same network interface. For example,

if one host connects to subnet A via LAN 1, the other host also must connect to subnet A via

LAN 1.

Note: NTP service will be automatically enabled on the active server once the high-availability cluster is created.

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Chapter 1: Introduction

Number of network ports

Both hosts must have the same number of LAN ports. If your host is equipped with additional

network interface cards, these network cards also count as additional LAN ports.

Note: With a hybrid high-availability cluster, you can have a different number of built-in network ports on each host. Refer to this article for more details.

Connection restrictions

The servers cannot connect to the network via IPv6, PPPoE, or Wi-Fi. Please make sure to

disable these functions before attempting to create a high-availability cluster.

Heartbeat connection

To ensure that the Heartbeat connection functions properly, the system will automatically

confirm and adjust certain connection configurations during cluster setup. Refer to the

information below for more details:

Other than the active and passive servers, there should be no other devices between the

Heartbeat connection.

We highly recommend you to connect the two hosts directly without passing through any

switches.

Make sure to use the fastest network interface on both hosts. For example, if one host is

equipped with an additional 10GbE network card, the connection must also use an additional

10GbE network card.

A Heartbeat connection can transfer Jumbo Frame packets to the other Synology NAS using

a specified network interface. If the connection passes through a switch, make sure that the

switch also supports Jumbo Frame.

A Heartbeat connection requires low latency, and its response time should be less than 1 ms.

The connection speed of the Heartbeat connection must be faster than 50MB/s.

If the Heartbeat connection bandwidth is insufficient, the upload speed will be affected.

Therefore, the bandwidth of the Heartbeat connection must be higher than the total sum of

the bandwidths of all cluster connections. We recommend you to choose the fastest network

interface, including Link Aggregation or 10G/40G network interface.

Notes:

With a Heartbeat connection, two IP addresses (e.g., 169.254.1.1 and 169.254.1.2) will be generated for data synchronization between the active and passive server. Make sure that these IP addresses are not occupied by other devices in the network.

The Heartbeat interface does not support VLAN ID.

Traffic control on a switch may cause packet loss. To avoid this, make sure that traffic control is set to auto.

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Chapter 1: Introduction

Link aggregation settings

Both servers must use the same link aggregation settings for the data network and the

Heartbeat connection. Once the high-availability cluster has been created, link aggregation

settings cannot be modified.

Notes:

If the Heartbeat connection is direct and does not pass through a switch, select IEEE 802.3ad Dynamic Link Aggregation or Balance XOR as the Link Aggregation mode. Otherwise, the Heartbeat connection may experience issues.

If the Heartbeat connection passes through a switch, select Adaptive Load Balancing or Balance XOR as the Link Aggregation mode and disable IEEE 802.3ad (Dynamic) Link Aggregation (LACP, 802.1AX) on the switch.

Once a high-availability cluster has been created, the bond selected for the Heartbeat connection will automatically enter round-robin mode to provide support for auto failover and load balancing. The bond will return to its initial configuration if the cluster is destroyed.

Open vSwitch settings

The status of Open vSwitch must be the same on both servers (enabled or disabled). Open vSwitch settings can still be modified after the high-availability cluster is created.

2.3 Limitations

Package and software limitations

Once the high-availability cluster is formed, the following packages and features will no longer

be available:

PetaSpace

Migration Assistant

The ability to restart/shut down the high-availability cluster in Synology Central Management

System (CMS).

The cluster feature for Virtual Machine Manager

The cluster feature for Synology MailPlus Server

Synology Directory Server should be configured after cluster creation. If you have already

installed Synology Directory Server prior to cluster creation, refer to the Create a cluster with a Synology NAS in use section for instructions.

USB device limitations

SHA does not support switchover/failover for USB devices. Any services or applications

provided by USB devices may not work properly after switchover/failover.

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Chapter 3: Set Up and Configure an SHA Cluster

3.1 Connect the hosts

To achieve broader bandwidth for the cluster and Heartbeat connections, we recommend you

to set up network interfaces as follows:

If you have four 1 GbE network interfaces available, set up dual-interface Link Aggregation

for the cluster and Heartbeat connections.

If you have two 10 GbE network interfaces available, we recommend you use one as the

cluster connection and the other as the Heartbeat connection.

This section explains how to connect the hosts to create a high-availability cluster.

1. Use a network cable to connect the two hosts. This connection will serve as the Heartbeat

connection between the two hosts and assist with communicating and copying data from

the active (primary) server to the passive (secondary) server. This connection must meet

the requirements listed in the Heartbeat connection section of Chapter 2: Required environment > System requirements > Network environment.

Chapter 3: Set Up and Configure an SHA Cluster

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Chapter 3: Set Up and Configure an SHA Cluster

2. Use a network cable to connect the two servers to the network through the remaining

network interface. Make sure that these connections are functioning properly and belong

to the same network. To avoid service interruptions caused by network disconnection, we

recommend you to use multiple switches in the network environment.

3. The hosts are now ready to create a high-availability cluster. Continue on to the following

section.

3.2 Create a cluster

Create a cluster with two new Synology NAS

This section provides instructions on how to create a high-availability cluster using two new

Synology NAS. For example, we will use two brand-new DS1621+ Synology NAS, Server A

(active) and Server B (passive). In this example, the cluster is created before the creation of

any volumes. Using two different models (hybrid high-availability cluster) may have an impact

on the cluster. Refer to this article for more details.

1. If needed, go to Control Panel > Network > General to edit the Server name on each

device.

2. Go to Control Panel > Network > Network Interface, select a network interface for

the Heartbeat connection and click Edit. Then, select Get network configuration automatically (DHCP). Click OK when done.

3. The IP address of both servers must belong to the same subnet and must be assigned static

IP addresses. To assign a static IP address, select the network interface, click Edit, select

Use manual configuration, and then enter the required information. Refer to the following

settings for example:

Server A

Server name: NAS-A

LAN 1: DHCP IP address

LAN 2: Static IP address 10.17.196.12

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Chapter 3: Set Up and Configure an SHA Cluster

Server B

Server name: NAS-B

LAN 1: DHCP IP address

LAN 2: Static IP address 10.17.196.13

4. On each server, go to the Package Center and install Synology High Availability.

5. Sign in on the host that you want to assume the role of the active server (Server A) with an

account belonging to the administrators group.

6. Open Synology High Availability.

7. Click Create high-availability cluster to open the cluster creation wizard.

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Chapter 3: Set Up and Configure an SHA Cluster

8. Read the content of the Before you start page carefully. After confirming that the

configurations of your two servers meet the requirements, click Next.

9. If the recommended network configuration meets your needs, configure your network

according to the recommendations.

10. Select the network interfaces for the Cluster connection and Heartbeat connection. For

example, we used LAN 2 for the cluster interface and LAN 1 for the Heartbeat interface.

Click Next.

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Chapter 3: Set Up and Configure an SHA Cluster

11. Enter the credentials of an account belonging to the administrators group for the passive

server. Click Next.

12. Specify a name for the high-availability cluster and the IP address that you will use to

access the cluster. The cluster IP must be in the same subnet as both servers and must be a

Static IP. Do not use a DHCP IP. Click Next when youre done. We used the following name

and IP address for example:

Cluster Hostname: NAS-HA

Cluster Static IP address: 10.17.196.14

13. The wizard will check if your system meets the requirements. Click Next once the

verification is complete.

14. Confirm your settings and click Done.

15. Tick the checkbox after reading the instructions and click Yes.

16. The wizard will start creating the high-availability cluster. The time needed varies

depending on your environment.

During the cluster creation process, do not power off the active server or the passive

server. If a power failure occurs during the cluster creation process, the cluster will fail to

be created.

17. Once the process is complete, you can access the data and services via the new cluster

hostname and IP address.

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Chapter 3: Set Up and Configure an SHA Cluster

Notes:

You can use Synology Assistant to check the status of the cluster by searching for your Synology NAS. You can only see the cluster Hostname and cluster IP address after the cluster is created.

You can access shared folders and services via cluster Hostname or cluster IP address.

Once the cluster is created, the passive server will no longer actively provide services, but will remain in standby mode.

You can manage the cluster in Synology High Availability. Refer to Chapter 4: Navigate the SHA User Interface for more information.

Create a cluster with a Synology NAS in use

This section explains the process of creating a high-availability cluster with a Synology NAS that

youre already using.

For example, you already have a Synology DS1621+. After the device has been used for a

period of time, you purchase another brand new DS1621+ to create a high-availability cluster.

The process of creating a high-availability cluster with Synology NAS in use is mostly the same

as creating a cluster with two new Synology NAS. However, there are a few key differences

to keep in mind:

1. Make sure that the existing environment meets the requirements as defined in Chapter 2: Required environment.

2. Synology High Availability does not support Synology NAS implemented with SHR (Synology

Hybrid RAID). If you have already set up SHR on your existing Synology NAS, make sure to

remove the SHR storage pool before you proceed to create a high-availability cluster. The

RAID type of SHR storage pools cannot be changed directly to other non-SHR RAID types.

Follow the steps below to back up the data, create a new storage pool of other RAID types,

and then restore the data on the new storage pool.

a. Back up the storage pool. Refer to this article for instructions.

b. Go to Storage Manager > Storage and select the SHR storage pool you want to remove.

c. Click Remove.

d. Create a new storage pool and select a non-SHR RAID type. Refer to the respective help

articles for DSM 7.0 and DSM 6.2 for instructions.

e. Create one or more new volumes. Refer to the respective help articles for DSM 7.0 and

DSM 6.2 for instructions.

f. Restore the backed-up data to the newly created storage pool and volume. Refer to this article for instructions.

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Chapter 3: Set Up and Configure an SHA Cluster

3. High-availability clusters must be created before you install Synology Directory Server. If

you already have Synology Directory Server installed, follow the steps below to back up its

data and configurations and then uninstall/reinstall the package.

a. Back up Synology Directory Server using Hyper Backup. Refer to the respective articles

for DSM 7.0 and DSM 6.2 for more instructions.

b. Go to the Package Center and uninstall Synology Directory Server.

c. Create a high-availability cluster.

d. Reinstall Synology Directory Server and restore the package data and configurations

using Hyper Backup. Refer to the respective help articles for DSM 7.0 and DSM 6.2 for

instructions.

4. Once youve created the cluster, you will be redirected to the main page, and the system will

perform the initial synchronization. All data on the active server will be fully synchronized to

the passive server.

Note: Do not use the original Hostname or IP address of the active server to access your Synology NAS. If services are transferred to another server after a failover, the original active server will become the passive server. If you continue to use the original device's Hostname or IP address, you will not be able to access the device's services in the event of a failover.

Add a passive server to an existing cluster

This section explains the process of adding a passive server to a existing cluster. For example,

the active server currently in use and the passive server to be added to the cluster are both

DS1621+. These servers will be referred to as Server A and Server B, respectively.

1. Refer to steps 1-4 in Create a cluster with two new Synology NAS to set up your passive

server (Server B).

2. Sign into the active server with an account belonging to the administrators group.

3. Open Synology High Availability.

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Chapter 3: Set Up and Configure an SHA Cluster

4. Click + to add the passive server.

5. Click Yes to open the cluster creation wizard. Services on the active server will continue

during cluster creation.

6. Read the content of the Before you start page carefully. After confirming that the

configurations of the two servers meet the requirements, click Next.

7. The cluster interface and Heartbeat interface will be based on the settings of the existing

active server. If you want to change the cluster or Heartbeat interface, you will have to

remove the high-availability cluster, reconfigure the network settings of the two hosts, and

then re-create the high-availability cluster. Click Next.

8. Enter the credentials of an account belonging to the administrators group on the passive

server. Click Next.

9. The wizard will check if your system meets the requirements. Click Next when complete.

10. Confirm your settings and click Done.

11. Tick the checkbox after reading the instructions and click Yes.

12. The wizard will start creating the high-availability cluster. The time needed varies

depending on your environment.

During the process of adding the passive server, do not power off the active server or the

passive server. If a power failure occurs during the cluster creation process, the cluster

will fail to be created.

13. Once completed, you will be redirected to the main page. The cluster status will show that

the data is being synchronized.

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Chapter 3: Set Up and Configure an SHA Cluster

3.3 Tests and simulations

SHA's failover mechanism is the key to minimizing service interruption resulted from system

malfunctions. To ensure your disaster recovery plan is robust and tested, you can simulate

disaster scenarios to assess your SHA setup.

Before you start

Make sure you have backed up any important data. Your devices may get disconnected while

running tests, which could result in data loss.

Sign in to DSM using the cluster IP address. We do not recommend using the active server IP

address to sign in, and the passive server IP address is unavailable.

If a problem occurs during the testing process that causes the cluster or a server to be

removed, you can sign in to DSM again using the active servers IP address.

Manual switchover and automatic failover

A switchover can be manually triggered for system maintenance with little service

interruption. An auto-failover can be triggered by various events. When certain errors occur

(such as network unavailability, software error, hard disk damage, RAID damage, etc.), the

system can automatically initiate a failover of services from the active to the passive server to

maximize availability.

To trigger a switchover:

On the Cluster page, confirm that the status of the cluster is Healthy, and then click Manage

> Switchover. The servers in the cluster should exchange roles: the original active server

will assume the role of the passive server, while the original passive server will take over the

provision of services to become the active server.

To trigger an auto-failover:

On the Cluster page, confirm that the status of the cluster is Healthy, and then recreate one

of the following events to induce an error and trigger auto-failover:

Remove the power source from the active server to simulate a power outage.

Disconnect the active server from the Cluster connection to simulate network failure. Do not disconnect the Heartbeat connection.

Refer to this article for step-by-step instructions on how to manually initiate a switchover,

trigger an auto-failover, or simulate connection problems.

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Chapter 3: Set Up and Configure an SHA Cluster

Split-brain error simulation and solutions

A split-brain error occurs when there is an interrupted connection between the Heartbeat

and Cluster connections. Both the active and passive servers will try to assume the role of the

active server and result in a split-brain. This may lead to data inconsistencies on the servers

and must be resolved as soon as possible. For more information on split-brain, you can refer

to the Split-brain section of Chapter 4: Navigate the SHA User Interface.

This section demonstrates how to test and solve the split-brain error. Since the testing process

will affect the status of the cluster, we recommend you to do this when the cluster is not

providing services.

Enter Safe Mode (Split-brain Mode) 1. Go to Control Panel > Shared Folder to create a shared folder (Share1). Upload some test

files (1.txt and 2.txt) to Share1 through File Station.

2. Quickly unplug all cables from the active server (NAS-A). Services will be temporarily

unavailable.

3. The system will notice that the active server (NAS-A) is unavailable and perform auto-

failover to the passive server (NAS-B). The passive server (NAS-B) will become the active

server and start providing services.

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Chapter 3: Set Up and Configure an SHA Cluster

4. Sign in to NAS-B using the high-availability cluster IP address. The high-availability cluster

status will show that NAS-B is the active server and NAS-A is undetectable. In this case,

NAS-A and NAS-B are both acting as the active server.1

5. Make some changes to the data in the shared folder Share1 of NAS-B to create differences

(data inconsistencies) between the files on each server.

6. After about ten minutes, reconnect NAS-As Heartbeat interface and the primary cluster

interface network cable. Once NAS-A and NAS-B are reconnected, the system will start to

consolidate the data. When the system discovers that the data is inconsistent (split-brain

error), the High Availability cluster will enter Safe Mode.

7. After waiting some time, sign in to DSM (NAS-A) via one of the servers IP address. You will

see that the high-availability cluster status displays Split-brain error.

Notes:

1. If you do not see the split-brain error status, it means that the simulation was unsuccessful. Plug your devices back in and follow the steps from the beginning of this section to try again.

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Chapter 3: Set Up and Configure an SHA Cluster

Solve the split-brain error 1. Sign in to DSM (NAS-A) via the cluster IP address.

2. Services on both the servers and the IP addresses of the high-availability cluster will be

unavailable until the split-brain error is resolved.

3. A new tab named Split-brain will appear on the left panel. On this tab, the differences

between the files in the shared folders on the two servers and the time that the servers

became the active servers will be shown. Select the shared folder to compare from the

drop-down menu on the right.

4. File Station will be in read-only mode, so you will still be able to download or view the files.

5. On the Cluster tab, you can either shut down the cluster or resolve the split-brain error by

clicking the Manage button. There are two possible options. Refer to the the Split-brain

section of Chapter 4: Navigate the SHA User Interface for more details.

6. Select Keep data from only one of the servers and select NAS-B as the new active server.

7. Finish applying the settings. After a few minutes, you will be redirected to the Cluster page

and the cluster status will show that the data is being synchronized.

8. You can go to File Station to check again if the data of Share1 contains the most recent

data after the synchronization is complete.

3.4 Set up storage for SHA

Before you start

This user guide uses the following examples, which are based on SHAs minimum

requirements:

HDD: 2

Storage pool: RAID-1

Storage space / file system: Btrfs

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Chapter 3: Set Up and Configure an SHA Cluster

Notes:

Only RAID 1, RAID 5, RAID 6, RAID 10, RAID F1 and BASIC are supported.

Please install a brand new hard disk, as a used hard disk may encounter unexpected issues.

The storage settings will be synchronized on both the active and passive servers so that the settings on both servers will be the same.

Storage settings

1. Sign in to DSM using the cluster IP address and go to Storage Manager.

2. Go to Storage and click Create Now > Start.

3. Configure the storage pool properties and select RAID 1 for the RAID Type.

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Chapter 3: Set Up and Configure an SHA Cluster

4. Select and deploy the two drives and click Next.

5. Select Perform drive check and click Next.

6. Allocate the capacity size and click Next.

7. Select Btrfs for the file system and click Next. For more information on file systems, refer

to this article.

8. Confirm your settings and click Apply.

9. Click OK to complete the storage pool creation.

10. If you want to create a second storage pool or volume, click Create.

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Chapter 3: Set Up and Configure an SHA Cluster

3.5 Monitored services

Select the services that you want to monitor with Synology High Availability. If a monitored

service fails on the active server, the system will fail over to the passive server as long as it is

operating normally.

3.6 Quorum server

Quorum servers can help reduce the possibility of split-brain errors. On the Service page,

you can assign another server as the quorum server, which will constantly connect to both

the active and passive servers. A gateway server or a DNS server would both be appropriate

examples for the quorum server, since they are able to connect to both the active and passive

servers. The quorum server is meant to provide Ping services only, so no applications are

required to be installed.

A quorum server will allow for the following situations:

If the passive server cannot connect to both the active and quorum servers, failover will not

be performed in order to prevent split-brain errors.

If the active server cannot connect to the quorum server while the passive server can,

switchover will be triggered in order to ensure better availability.

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Chapter 3: Set Up and Configure an SHA Cluster

Set up a quorum server

1. Go to Synology High Availability > Service.

2. Tick Enable quorum server and enter the IP address of the quorum server.

3. Make sure that the quorum server is always connected to both active and passive servers.

4. Click Test Connection to make sure that the quorum server is connected properly.

5. Click Apply.

3.7 UPS

SHA clusters allow you to set up an Uninterruptible Power Supply (UPS) for each device. If

there is a power failure, the active and passive servers will enter Safe Mode to reduce power

consumption and prevent data loss. You can also use different types of UPS for each server,

depending on your needs.

The following three types of UPS are supported by SHA:

SNMP UPS

USB UPS

Synology UPS server

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Chapter 3: Set Up and Configure an SHA Cluster

SHA UPS behavior

We recommend using different power supplies for each server in the cluster to set up UPS. You

can choose a suitable type of UPS according to the equipments requirements. If something

happens to the power supply, UPS will help prevent the Synology NAS from powering off

unexpectedly.

If the active server experiences issues with its power supply, the active server will enter Safe Mode once the specified waiting period has been reached. The system will then switch services

over to the passive server so that they can run without interruption.

If the passive server experiences issues with its power supply, the passive server will enter

Safe Mode alone and not affect services on the active server. Once the power issue is resolved,

the passive server will automatically restart and return to the cluster to continue synchronizing

data.

If your environment does not allow for different power supply sources or the connection of

different UPS, you can connect any type of UPS to one of the servers. For example, connect

either the active server or the passive server to the UPS. If a power supply interruption occurs,

the server connected to the UPS will receive the notification of power failure and forward the

notification to the server that is not connected to the UPS. The two servers will then both enter

Safe Mode until power is recovered. Then, they will automatically restart to continue providing

high-availability services.

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Chapter 3: Set Up and Configure an SHA Cluster

SHA UPS configurations

If the two servers are connected to the same network switch

Connect the server to the same power source as the network switch and set up any type of

UPS (USB UPS / SNMP UPS / Synology UPS server) as the power source protection.

If you use USB UPS, connect the communication terminal to one of the servers. The server will

serve as the main receiving end-point. In this case, if a power failure occurs, the entire cluster

will enter Safe Mode.

If you use a SNMP UPS or Synology UPS server, you can connect one or both of the servers to

the same UPS. In this case, if a power failure occurs, both servers will enter Safe Mode.

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Chapter 3: Set Up and Configure an SHA Cluster

If the two servers can be connected to different power sources and network switches

We recommend you to connect the active server and the passive server to the power supply of

the corresponding network switch. You can set up one or two UPS types (USB UPS / SNMP UPS

/ Synology UPS server).

If you use USB UPS, connect the communication interfaces of the two UPS to the active server

and the passive server, respectively.

If you use SNMP UPS or Synology UPS server, you will need to set up a corresponding UPS IP

address for each server. In this case, if there is a problem with one of the power supplies, the

connected server will enter Safe Mode. If the power supply is that of the active server, services

will fail over to the passive server.

Note: For more information on UPS configuration, refer to the respective help articles for DSM 7.0 and DSM 6.2.

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3.8 Power schedule

At Control Panel > Hardware & Power > Power Schedule, you can click Create to add a

schedule for the system to automatically start up or shut down.

Note: Make sure that the power supply of the two servers is normal when the servers are scheduled to start up. When the two servers start up, the original role settings (active/ passive) will remain the same. If a power failure occurs on the active server and only the passive server is powered on, the passive server will not take over services to avoid a Split- brain error.

3.9 System notifications

If a major event or problem occurs in the system, you may want to be notified as soon as

possible. This section provides instructions for notifications settings.

Enable email notifications

1. Go to Control Panel > Notification > Email.

2. Tick Enable email notifications.

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Chapter 3: Set Up and Configure an SHA Cluster

3. Enter one or more email addresses in the Recipient's email address field. System

notifications will be sent to the addresses entered here. Ten addresses are allowed. You can

separate multiple addresses with a semi-colon (;).

4. If necessary, add a subject prefix in the Subject prefix field. This prefix will be added to

the subject of each message sent by your Synology NAS, helping you identify and filter

messages.

5. Refer to the respective help articles for DSM 7.0 and DSM 6.2 for more information.

Notification content settings

At Control Panel > Notification > Rules, you can select which types of events will trigger the

system to send notification messages, as well as the medium (e-mail, SMS, mobile devices,

DSM, and web browsers) through which you receive messages.

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Chapter 4: Navigate the SHA User Interface

To learn more about how to navigate the SHA User Interface, you can refer to the respective

help articles for DSM 7.0 and DSM 6.2.

4.1 Cluster

The Cluster page provides an overview of your SHA cluster. This page is divided into four

sections, offering you details on the cluster status, host utilization, and recent system logs. You

can also manage the cluster on this page.

Refer to the respective help articles for DSM 7.0 and DSM 6.2 for more details.

High-availability cluster status

The top of the page displays the overall status of the high-availability cluster. You can check

if the system is running as expected. Some solutions will be provided if there are system

abnormalities.

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Chapter 4: Navigate the SHA User Interface

Status Description

Healthy The cluster is healthy. Data is being replicated between the hosts. The auto- failover feature is available.

Processing The system is processing certain operations, such as data replication, volume repair/expansion, or others. The auto-failover feature is not available.

Updating The system or the package is updating. The auto-failover feature is not available.

Warning The system has detected errors in the cluster, but the services may still be running. The auto-failover function may be unavailable. Any errors must be addressed as soon as possible.

Critical

The system has detected one or more critical errors in the cluster, and the hosts are not able to run the usual services. All errors must be addressed as soon as possible. The system may encounter a split-brain error, where it may fail to determine which of the hosts is the active server. In this case, all services will be suspended to avoid further data inconsistencies until the issues are resolved.

To troubleshoot abnormal high availability cluster statuses (Warning or Critical), refer to

Chapter 2: SHA Troubleshooting in the Synology High Availability (SHA) Troubleshooting Guide.

High-availability cluster information

This section provides basic information on the Cluster connection with a simulated

illustration. A warning/critical icon will be displayed if there is a system error. You can also view

the Heartbeat connection status, the transfer speed, and the latency in this section.

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Chapter 4: Navigate the SHA User Interface

If certain events or errors occur on either of the servers, a beeping sound will alert you. You

can click Beep Off to turn off the sound. Please note that the beeping sound will reoccur at

restart if the issue is not resolved. Click the power button to shut down or restart the cluster.

You can also click Manage to perform updates, switchovers, add or remove the passive server,

or remove the cluster entirely.

Notes:

Once a high-availability cluster is removed, you will have to fully re-synchronize your data to create a new one.

If you shut down or remove the passive server, the auto-failover function will be unavailable.

Host Utilization

In this grid, you can monitor the resource usage of the two hosts. The resource usage of the

hosts are correlated, however, the statistics of the active server are usually be higher since it is

responsible for running all services.

In this section, you can check the following:

CPU utilization and load average: To ensure that the system reserves sufficient resources

to monitor the cluster, we recommend that the CPU utilization is lower than 80%.

Memory usage: This indicates how much memory has been occupied. We recommend that

20% of the memory is reserved for system-related monitoring.

Drive activity: This information indicates if the drives are running data read/write activities

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Recent Important Events

The five most recent logs will be listed in this section for you catch up with the latest cluster

activities. This information includes the date and time, the user, and the event details. This

section is useful for when something happens and you would like to see the most recent

activities in the cluster. For complete log records, refer to the Log tab.

4.2 Host

The Host page displays crucial information about the two hosts. This includes the Find button

for locating your NAS via a beeping sound and LED light and the Power buttons for each

server. This page also shows each hosts information, along with their hardware statuses and

software versions. Refer to the respective help articles for DSM 7.0 and DSM 6.2 for more

details.

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4.3 Network

This page contains two tabs, one that provides the network settings of the high-availability

cluster and the other of the hosts. You can get an overview of the network interface usage and

create or remove additional Cluster connections if necessary.

Refer to the respective help articles for DSM 7.0 and DSM 6.2 for more details.

HA Cluster

Under General, you can view or edit the hostname of the cluster.

All network connections, regardless of whether they are used or unused, are displayed in

the Network field. At least one of the cluster interfaces is displayed here. Click the Manage Network Interface button to configure the clusters IP or network settings. The hosts IP

addresses and network settings can be configured by clicking Manage Network Interface >

Configure Server Network. The Heartbeat interface listed is the only Heartbeat connection

allowed in the cluster and cannot be managed.

Notes:

Make sure that all Ethernet cables are properly connected.

If you are unable to configure the network interface settings, please go to the Cluster page first to resolve any system abnormalities.

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Chapter 4: Navigate the SHA User Interface

Hosts

This tab shows the statuses and details of the network interfaces on the active and the passive

servers.

4.4 Service

This page allows you to monitor certain services. If a monitored service fails on the active

server, the system will fail over to the passive server as long as the passive server is operating

normally.

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Chapter 4: Navigate the SHA User Interface

Supported services

Windows File Service

iSCSI Target

FTP

Mac File Service

NFS Service

Synology Directory Server

Web Services

Refer to the respective help articles for DSM 7.0 and DSM 6.2 for more details.

Quorum Server

Quorum servers can help reduce the possibility of split-brain errors. Refer to the Quorum Server section of Chapter 3: Set Up and Configure an SHA Cluster for more information and

setup instructions.

4.5 Storage

This page details the statuses of the storage volumes on the active and passive servers in the

high-availability cluster. Refer to the respective help articles for DSM 7.0 and DSM 6.2 for more

details.

Because the capacity and configuration of volumes on the active and passive servers are

recommended to be identical, the volumes on the two servers are usually displayed together

in single units. Therefore, you must go to this page to view both the active and passive servers

volume statuses. However, the volumes on the active server are only viewable in Storage Manager when accessing a high-availability cluster.

Volume

This page contains information on the names, used capacity, available space, total capacity,

status, and other details about the volumes and iSCSI LUNs in the cluster.

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Chapter 4: Navigate the SHA User Interface

The following situations may require you to repair a malfunctioning volume or iSCSI LUN:

If a volume on one of the servers has crashed

If the passive server is offline

If a file system error occurs

You can use the Repair button in the case that you replaced a drive or if there is a file system

error. For more details on solving these issues, refer to the respective help articles for DSM 7.0 and DSM 6.2.

HDD/SSD

This tab provides the status and details on the drives. You can select a drive and click Health Info to view its statistics, run a S.M.A.R.T. test, and check its history.

Note: Do not change a drive's position once a volume has been created. This may risk you losing the volume.

4.6 Log

The Log page monitors and records the events of the high-availability cluster. You can view,

search for, sort, clear, and export logs.

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Chapter 4: Navigate the SHA User Interface

4.7 Split-brain

When a high-availability cluster is functioning normally, only one of the hosts should act as the

active server. The passive server detects the active server via the Heartbeat and the Cluster

connections. You can set up multiple paths to connect the hosts to the data network to achieve

data redundancy, but if the Heartbeat connection and the primary Cluster connection were

both to fail, both servers may attempt to assume the role of the active server and result in a

"split-brain" error.

In this case, connections to the IP addresses of the high-availability cluster will be redirected

to either of the two servers, causing inconsistent data to be written. Once either of the

connections is reconnected, the system will detect the split-brain error and the data

inconsistency between the hosts.

If you want to simulate a split-brain error on your SHA cluster, refer to the Split-brain error simulation and solutions section of Chapter 3.3: Tests and simulations.

Resolve a split-brain error

1. Reconnect the Heartbeat and Cluster connections.

2. Connect to either of the servers with the cluster IP address and open Synology High Availability.

3. To view the differences in the data on the two servers before resolving the split-brain error,

go to the Split-brain page and select the shared folder you want to compare.

The system may take some time to check the files. If you need to solve the split-brain

error as soon as possible, skip this step and select Keep all data of both servers in the

next step. To compare the data, follow the instructions in this article.

4. Click Manage > Resolve split-brain errors on the Cluster page and follow the onscreen

instructions. There are two options to choose from:1

Keep all data of both servers: Choose one host as the new active server and remove the

other. The new active server will still be in the cluster. The removed host will keep its data

and return to standalone status. A full data synchronization is required the next time you

add a passive server.

Keep data from only one of the servers: Choose one of the hosts as the new active

server. The system will sync the data and settings on the new active server to the new

passive server.2

Notes:

1. Make sure both hosts in the cluster are powered on before you choose the new active server when resolving the error. Shutting down the cluster does not solve the error. The split-brain error will remain until you address it using the methods mentioned in this article.

2. The changes made on the passive server during the split-brain will be lost if you choose this option.

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Chapter 5: Maintain your High-availability Cluster

5.1 Software updates

Synology periodically releases DSM and package updates that you can install on your high-

availability cluster. We recommend keeping the operating system and installed packages as

up-to-date as possible. These updates may include new features and function improvements,

but more importantly may offer critical bug fixes and security patches.

Before you start

Make sure that any system errors have been resolved and the SHA cluster status is Healthy.

Although updating DSM will not affect the data on your Synology NAS, we strongly

recommend you to back up your data before proceeding.

Update DSM on a high-availability cluster

The system starts DSM update on the passive server first. It may take between five and ten

minutes for the system to complete the process and restart the passive server. Services will

remain uninterrupted on the active server during this process. Once the passive server is

updated and back online, the system will perform a switchover to exchange the roles of the

active and the passive server.1

After the switchover is complete, the system proceeds to update the new passive server

(original active server). Services will remain uninterrupted on the new active server (original

passive server) during this process. Once the new passive server is updated and back online,

the system will perform a switchover again, returning the cluster to its original state.

To update DSM on a high-availability cluster: 1. Go to Synology High Availability > Cluster.

2. Click Manage and select Update DSM from the drop-down menu. This option will be

unavailable if the cluster is not healthy or not ready for a DSM update.

3. Click Yes to be redirected to the Update & Restore page in Control Panel.

4. Your Synology NAS will check if there is a new version available. If there is a new version

available, click Download and then click Update Now to begin the update process.2

To update DSM manually on a high-availability cluster: 1. Go to Synology Download Center, select your model, and click Download next to the DSM

version you need.

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Chapter 5: Maintain your High-availability Cluster

2. Go to Synology High Availability > Cluster.

3. Click Manage and select Update DSM from the drop-down menu. This option will be

unavailable if the cluster is not healthy or not ready for a DSM update.

4. Click Yes to be redirected to the Update & Restore page in Control Panel.

5. Click Manual DSM Update.

6. Upload the DSM update file you got from the Download Center and click OK to begin the

update process.

To update DSM manually on a hybrid high-availability cluster:

If you are using two different Synology NAS models to create a hybrid high-availability cluster, you can only update DSM manually.

1. Go to Synology Download Center, select the model, and click Download next to the latest

DSM version. Make sure to download the appropriate update file for each model.

2. Go to Synology High Availability > Cluster.

3. Click Manage and select Update DSM from the drop-down menu. This option will be

unavailable if the cluster is not healthy or not ready for a DSM update.

4. Click Yes to be redirected to the Update & Restore page in Control Panel.

5. Click Manual DSM Update.

6. Upload the DSM update file to each server and then click OK to begin the update process.

Update the Synology High Availability package

Services will still be available while updating the Synology High Availability package.

1. Go to Synology High Availability > Cluster.

2. Click Manage and select Update Package from the drop-down menu. This option will be

unavailable if the cluster is not healthy or not ready for an update.

3. Click Yes to be redirected to the Synology High Availability page in the Package Center.

4. If a newer version of the package is available, click Update to start the installation process.

Notes:

1. The system will only update one Synology NAS if there is no passive server in the high- availability cluster.

2. Available updates may vary depending on your current DSM configurations.

3. Both the active and the passive servers must be installed with the same DSM and Synology High Availability package versions.

4. Depending on the number of connections or services, the time the system takes to complete the update may vary.

5. Do not remove the power source, shut down the system, or disconnect any of the servers in the high-availability cluster while the system is updating.

6. You can safely shut down the cluster or individual servers after the update is complete and the cluster status is Healthy.

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5.2 Drive firmware update

If you installed Synology drives (HDD/SSD) in your high-availability cluster, you can update

their firmware via DSM. Firmware updates ensure the compatibility and continued use of the

Synology drives installed in your Synology NAS. If the firmware status of one or more drives in

DSM > Storage Manager > HDD/SSD is Update required, please proceed with the update.

1. In Storage Manager, go to the HDD/SSD page.

2. Select a Synology drive and click Action > Firmware Update.

3. Click Update.

Notes:

We strongly recommend you to first back up the data on the selected Synology drives before updating their firmware.

If the Synology drives are in use (e.g., assigned to a storage pool or as hot spares), a system restart will be required in order to halt all services during the update and prevent any application errors.

You can perform firmware updates for Synology drives on both servers from the active server.

5.3 Network management

Modify the IP addresses of servers or the cluster

Synology High Availability (since version 2.0.2) allows you to modify the IP addresses of the

network interfaces on the active and the passive servers without removing the cluster. You can

also modify the IP address of the cluster.1

1. Go to Synology High Availability > Network, and click Manage Network Interface.

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2. You can edit, enable, and disable2 the SHA cluster IP address, or click Configure Server Network to edit the IP addresses of the active and passive servers.

3. Select Use manual configuration and edit the network information of either or both

servers.

4. Click OK when youre done.

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5. Click Apply to save your settings.

Notes:

1. You can also modify the IP address of any bonded network interfaces, however, you cannot change the following:

Link Aggregation settings (e.g., Link Aggregation mode)

VLAN settings

Network interfaces of the Cluster connection and Heartbeat connection If you want to change these settings, you will have to remove the cluster and create a new cluster with new settings.

2. You cannot disable the cluster IP on the primary cluster interface.

Migrate the cluster to another network

1. Move your devices to the new network environment.

2. Open Synology Assistant1 on a computer within the new network environment.

3. Find the cluster via the cluster name (under Server Name), or the clusters original IP

address.

4. The status of the cluster should be Connection failed.

5. Right-click on the cluster and click Setup to configure the new network settings.

6. Enter a DSM administrators username and password.

7. Select Use manual configuration and specify the new IP information.

8. Click OK to save your settings.

9. Go to Synology Assistant again, and you will see that your clusters IP address has

changed.

10. Double-click on the cluster and sign in.

11. You can modify other network settings by going to Synology High Availability > Network.

Notes:

1. To download Synology Assistant, go to Synology Download Center, select your model, click on the Desktop Utilities tab, and click Download next to Synology Assistant.

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5.4 Storage capacity expansion

Expand the storage capacity by adding new drives

Before you start

Please note that only storage pools implemented with the following RAID types can be

expanded using this method: RAID 1, RAID 5, RAID 6, RAID 10, RAID F1.

1. Perform Data Scrubbing (DSM 7.0 / DSM 6.2) to check if your volume and storage pool are

normal. If the status is anything other than normal, make sure to repair it first.

2. Prepare drives that are listed on the Synology Products Compatibility List. Using

incompatible drives may lower system performance or cause data loss.

3. Back up your data. The expansion process will not delete any existing data, but we still

strongly recommend you to back up your data before proceeding.

4. In Storage Manager, do the following:

Go to HDD/SSD to check if the inserted drive is healthy.

Make sure the inserted drive meets the drive requirements. Go to HDD/SSD to check the

drive size and type.

Go to Storage (DSM 7.0) or Storage Pool (DSM 6.2) to check if the storage pool status is

healthy.

5. Make sure your Synology NAS model supports using drives located in expansion units. For

more information, refer to this article.

6. Make sure the maximum total capacity of the volumes and LUNs on your high-availability

cluster has not reached or exceeded 400 TB. For more information, refer to the Synology High Availability specifications.

Add new drives to a high-availability cluster 1. Insert new drives into identical empty slots on both the active and the passive servers. To

avoid injury or damaging your Synology NAS, make sure to follow the drive installation

instructions found in the Hardware Installation Guide for your Synology device.1

2. Make sure that all of the new drives show up in Synology High Availability > Storage >

HDD/SSD. You can check the status of the active or passive servers by selecting them from

the drop-down menu in the top-right corner of the page.

Expand storage capacity with Storage Manager 1. Go to Storage Manager to complete the final steps. Please note that the switchover

function will not be available at any time during these processes.

2. Do one of the following depending on your situation:

Expand an existing storage pool by adding drives. Refer to the respective help articles for

DSM 7.0 and DSM 6.2 for instructions.

Create a new storage pool. Refer to the respective help articles for DSM 7.0 and DSM 6.2

for instructions.

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Expand the storage capacity by replacing the drives with larger ones

Before you start 1. Make sure that your implemented RAID type allows drives to be replaced without causing

data corruption. Refer to the Choose a RAID Type help articles for DSM 7.0 and DSM 6.2

for more information.

2. Check the items for Before you start in the Expand the storage capacity by adding new drives section above.

Replace drives to expand storage capacity on the active server

Start with the active server. Do not remove the drives from both the active and the passive

servers at the same time. This will cause both servers storage spaces to become degraded. If

you plan to replace multiple drives, make sure to replace them one-by-one. After replacing one

drive, you must repair the storage pool before replacing the next one.2 3

1. Go to Storage Manager > Storage > Storage Pool to see which of the existing drives is the

smallest.

2. Remove a drive from the active server and replace it with one of a larger size. To avoid

injury or damaging your Synology NAS, make sure to follow the drive installation

instructions found in the Hardware Installation Guide for your Synology device.1

3. Go to Storage Manager > HDD/SSD to make sure the newly added drive has been

recognized.

4. Go to Storage Pool and select the storage pool. At this point, its status should be Degraded.

5. Repair the degraded storage pool.

DSM 7.0 and above: Click   and select Repair.

DSM 6.2 and earlier: Click Action > Repair.

6. Select the replacement drive to add to the storage pool. Follow the instructions in the

wizard to complete this step.

7. Repeat the process above one-by-one on the active server until all desired drives have been

replaced with larger ones.

Replace drives to expand storage capacity on the passive server

When replacing drives to expand the storage capacity of the passive server, make sure to

follow the same order and configurations performed on the active server.

1. Remove a corresponding drive from the passive server and replace it with one of a larger

size.

2. Go to Synology High Availability > Storage > HDD/SSD to make sure the newly added

drive has been recognized.

3. Go to the Volume tab. At this point, the status should be Degraded.

4. Select the degraded volume and then click the Repair button.

5. Repeat the process above until the drive configurations of the passive server and active

server are the same.

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Expand storage capacity with Storage Manager

Once all of the desired drives on both active and passive servers have been replaced and

repaired, go back to Storage Manager to complete the final steps.

1. Go to the Storage Pool tab and select the storage pool to be expanded.

DSM 7.0 and above: Click   and select Expand.

DSM 6.2 and earlier: Click Action > Expand.

2. Click Apply to confirm the settings.

Notes:

1. Your devices Hardware Installation Guide can be found in the Synology Download Center under Documents.

2. When replacing drives of RAID 5 / RAID 6 / RAID 10 / RAID F1 storage pools, the smallest drive should always be replaced first in order to maximize drive usage. The storage capacity of each RAID type is as follows:

RAID 5: (number of drives 1) x (smallest drive size)

RAID 6: (number of drives 2) x (smallest drive size)

RAID 10: (number of drives / 2) x (smallest drive size)

RAID F1: (number of drives 1) x (smallest drive size)

3. Do not initiate a switchover at any time during this process.

Expand the storage capacity with Synology expansion units

Synology expansion units are designed for pairing with specific expansion-ready NAS products

to increase their internal volume or form independent volumes for backup or additional

storage. When you use two expansion-ready NAS in a high-availability cluster, you will be able

to expand its storage capacity with expansion units. Refer to this article to see if your servers

are compatible with Synology expansion units.

This section provides steps on pairing expansion units with your high-availability cluster. To do

this, you must be have two identical expansion units for both the active and passive servers.

For example, we will use two DS1621+ (active and passive servers) and two DX517 (expansion

units).

1. Install your drives on the two DX517 models. The drive capacities, number of drives, and the

slot positions must be identical on each device.

2. Plug both DX517 devices into power outlets.

3. Connect the Synology eSATA expansion cables to the expansion ports of the DX517 and

DS1621+ devices. We strongly recommend using Synology expansion cables. We do not

recommend using other expansion cables.

4. Once the connections are made, the DX517 devices will turn on automatically whenever

their connected NAS powers on. Do not remove the expansion cable while the host device

is powered on. Doing this may result in data loss.

5. Sign in to your high-availability cluster and go to Storage Manager > Overview to see if the

expansion unit has been successfully connected.

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6. You can now do the following:

Create a storage pool on the expansion units. Refer to the respective articles for DSM 7.0

and DSM 6.2 for instructions.

Create a volume. Refer to the respective articles for DSM 7.0 and DSM 6.2 for instructions.

5.5 Memory expansion

Overall Synology server performance, such as data transmission speed and system response

when multi-tasking, can be enhanced by expanding the memory capacity. Refer to this article

for more information on Synology NAS memory expansion. This section briefly introduces two

methods that you can use to expand the memory of your high-availability cluster.

Before you start

Make sure that the memory capacity of the two servers is exactly the same to ensure that

services can be properly transferred and to maintain consistent system performance.

Go to the Download Center and download the Hardware Installation Guide for your

Synology NAS.

Method 1: Shut down the cluster

You can expand the memory capacity on your active and passive servers, but you will need to

shutdown the cluster for a short period of time.

1. Sign in to your high-availability cluster and go to Synology High Availability > Cluster.

2. Click the power button and select Shut down cluster.

3. Refer to the information in the Hardware Installation Guide to install memory modules

on both servers.

4. Power on each device in the cluster by pressing their power buttons.

5. Sign in to your high-availability cluster.

6. Go to Synology High Availability > Host to confirm that the memory modules have been

expanded on both servers.

Method 2: Switchover

You can reduce service downtime when installing memory modules by utilizing the switchover

function.

1. Sign in to your high-availability cluster and go to Synology High Availability > Host.

2. On the passive server, click the power button and select Shut Down.

3. Refer to the information in the Hardware Installation Guide to install the memory module

on the passive server.

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4. Power on the passive server by pressing its power button.

5. Sign in to your high-availability cluster.

6. Go to Synology High Availability > Host to confirm that the memory modules on the

passive server have been expanded.

7. On the Cluster page, click Manage > Switchover.

8. Perform steps 1-6 again on the other server to install the memory module.

Note: If you've configured an SSD cache, Synology High Availability may encounter memory inconsistency during the expansion process. This is a normal phenomenon. Once the subsequent steps are completed, the memory capacity will be consistent again and the status will return to normal. For more details, refer to Chapter 2: SHA Troubleshooting in the Synology High Availability (SHA) Troubleshooting Guide.

5.6 M.2 SSD installation

SSD caches can achieve better performance on Synology NAS by leveraging the advantages

of SSDs. By storing frequently accessed data in an SSD cache, you can reduce I/O latency and

improve the system performance of your Synology NAS. Refer to this article to see if you can

install M.2 SSDs on your active and passive servers. This section introduces two methods that

you can use to install M.2 SSDs on your high-availability cluster.

Before you start

Make sure that the M.2 SSD capacity of the two servers is exactly the same to ensure that

services can be properly transferred and to maintain consistent system performance.

Go to the Download Center and download the Hardware Installation Guide for your

Synology NAS.

Method 1: Shut down the cluster

You can install M.2 SSDs on your active and passive servers, but you will need to shutdown the

cluster for a short period of time.

1. Sign in to your high-availability cluster and go to Synology High Availability > Cluster.

2. Click the power button and select Shut down cluster.

3. Refer to the information in the Hardware Installation Guide to install the M.2 SSDs on

both servers. Make sure you install the M.2 SSDs in identical slots on both servers.

4. Power on each device in the cluster by pressing their power buttons.

5. Sign in to your high-availability cluster.

6. Go to Synology High Availability > Storage > HDD/SSD to confirm that the M.2 SSDs have

been successfully installed.

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Method 2: Switchover

You can also reduce the service downtime when installing M.2 SSDs by utilizing the switchover

function.

1. Sign in to your high-availability cluster and go to Synology High Availability > Host.

2. On the passive server, click the power button and select Shut Down.

3. Refer to the information in the Hardware Installation Guide to install the M.2 SSDs on the

passive server. Make sure that you install the M.2 SSDs in identical slots on both servers.

4. Power on the passive server by pressing its power button.

5. Sign in to your high-availability cluster.

6. Go to Synology High Availability > Storage > HDD/SSD to confirm that the M.2 SSDs have

been successfully installed on the passive server.

7. On the Cluster page, click Manage > Switchover.

8. Perform steps 1-6 again on the other server to install the M.2 SSDs.

5.7 Network interface card installation

This section provides two methods that can be used to install a network interface card.

Before you start

Go to the Download Center and download the Hardware Installation Guide and

Datasheet for your Synology NAS. Then, check the following:

Make sure that the PCIe slot is supported on your Synology NAS.

Confirm that the network interface card you want to use is listed on Synology Products Compatibility List.

Make sure that the number of network ports on both servers is the same.

Method 1: Shut down the cluster

You can install network interface cards on your active and passive server, but you will need to

shut down the cluster for a short period of time.

1. Sign in to your high-availability cluster and go to Synology High Availability > Cluster.

2. Click the power button and select Shut down cluster.

3. Refer to the Hardware Installation Guide for instructions on how to install the network

interface cards on both servers.

4. Power on each device in the cluster by pressing their power buttons.

5. Sign in to your high-availability cluster.

6. Go to Synology High Availability > Network > Hosts to confirm that the network interface

cards have been successfully installed.

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Chapter 5: Maintain your High-availability Cluster

Method 2: Switchover

You can also reduce the service downtime when installing network interface cards by utilizing

the switchover function.

1. Sign in to your high-availability cluster and go to Synology High Availability > Host.

2. On the passive server, click the power button and select Shut Down.

3. Refer to the Hardware Installation Guide for instructions on how to install the network

interface card on the passive server.

4. Power on the passive server by pressing its power button.

5. Sign in to your high-availability cluster.

6. Go to Synology High Availability > Network > Hosts to confirm that the network interface

card has been successfully installed.

7. On the Cluster page, click Manage > Switchover.

8. Perform steps 1-6 again on the other server to install the network interface card.

5.8 Data migration

If you purchase a new Synology NAS, your existing data can be moved from an old Synology

NAS to the new one via a process called migration. This section introduces data migration

methods that can be used in a high-availability cluster. These methods allow you to replace the

servers in the cluster without losing the original cluster data.

Before you start

Performing migration moves data and drives from one Synology NAS to another. In this

section, the following terms are used:

Source Synology NAS: The original Synology NAS from which data is moved.

Destination Synology NAS: The Synology NAS to which data is moved.

Make sure both the source and destination Synology NAS are running the same version of

DSM.

Make sure that the drives and Ethernet cable configurations are the same on the source and

destination Synology NAS.

Make sure that the two servers are the same models or are supported hybrid high-

availability models after being migrated to the new Synology NAS. Refer to this article for

supported hybrid high availability model combinations.

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Chapter 5: Maintain your High-availability Cluster

Refer to the table below for some examples of different model combinations.

Original Model Combination Migration New Model Combination

Active Server: DS918+

Passive Server: DS918+

Migrate active server data

Migrate the active server from DS918+ to DS920+.

Active Server: DS920+

Passive Server: DS918+

Active Server: DS920+

Passive Server: DS918+

Migrate passive server data

Migrate the passive server from DS918+ to DS920+.

Active Server: DS920+

Passive Server: DS920+

Active Server: DS920+

Passive Server: DS918+

Migrate cluster (active and passive server) data

Migrate the active server from DS920+ to RS3621xs+.

Migrate the passive server from DS918+ to RS3617xs+.

Active Server: RS3621xs+

Passive Server: RS3617xs+

Migrate passive server data

This section outlines the process of migrating data from the passive server. You can refer to

this article for detailed information on DSM migration.

1. Go to Synology High Availability > Host. Click the power button for the passive server and select Shut down.

2. Remove the drives and disconnect the Ethernet cables from the source Synology NAS.

3. Install the drives on the destination Synology NAS. Drives must be installed in the same

order as they were installed on the source Synology NAS.

4. Connect the Ethernet cables to the destination Synology NAS. Ethernet cables must be

connected to the same ports as they were on the source Synology NAS.

5. Power on the destination Synology NAS (new passive server).

6. Open a web browser on your computer and go to find.synology.com.

7. Find the destination Synology NAS. Its status should be Migratable or Recoverable.

8. Double-click on the destination Synology NAS to start the migration process.

9. Follow the wizard to complete the migration process. Make sure that you install the same

DSM version as the one used on the active server.

10. Once the migration is complete, the destination Synology NAS will automatically be

restarted and added to the cluster as the passive server. If you need to modify the new IP

address, refer to the Network management section of Chapter 5: Maintain your High- availability Cluster for instructions.

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Chapter 5: Maintain your High-availability Cluster

Migrate active server data

As long as the status of the cluster is Healthy, you can follow the steps below to migrate data

and replace the active server in your high-availability cluster. If the status of the cluster is

Abnormal, please troubleshoot the issue before you migrate your data and replace the server.

1. Go to Synology High Availability > Cluster, and click Manage > Switchover. This

exchanges the roles of the active and passive servers.

2. Perform steps in Migrate passive server data section on the original active server (passive

server after completing step 1).

3. To make the destination Synology NAS the new active server, go to Synology High Availability > Cluster, and click Manage > Switchover again.

Migrate cluster (active and passive server) data

This section outlines the process of migrating data from both the active and the passive

servers in the cluster. You can refer to this article for detailed information on DSM migration.

1. Sign in to your high-availability cluster and go to Synology High Availability > Cluster.

2. Click the power button and select Shut down cluster.

3. Remove the drives and disconnect the Ethernet cables from both source Synology NAS

devices.

4. Install the drives on the destination Synology NAS devices. Drives must be installed in the

same order as they were installed on the source Synology NAS devices.

5. Connect the Ethernet cables on the destination Synology NAS devices. Ethernet cables must

be connected to the same ports as they were on the source Synology NAS devices.

6. Power on the destination Synology NAS for the new active server.

7. Open a web browser on your computer and go to find.synology.com.

8. Find the destination Synology NAS for the new active server. Its status should be

Migratable or Recoverable.

9. Double-click on the destination Synology NAS to start the migration process.

10. Follow the wizard to recover the active server first. Make sure to install the same DSM

version as was used on the source Synology NAS.

11. Once the migration is complete, the destination Synology NAS will automatically be

restarted and added to the cluster as the active server.

12. Perform steps 7-10 again for the passive server.

13. If you need to modify the new IP addresses, refer to the Network Management section of

Chapter 5: Maintain your High-availability Cluster for instructions.

Note: If the cluster is in an abnormal state before migration, refer to Chapter 2: SHA Troubleshooting in the Synology High Availability (SHA) Troubleshooting Guide to fix the issue before continuing.

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Related articles

Can I create a high-availability cluster with two different Synology NAS servers?

What should I know when creating a Heartbeat connection for a Synology High Availability cluster?

How long does it take to synchronize high-availability clusters?

What is the purpose of setting up a quorum server in a high-availability cluster?

Can I move the hard drives after setting up high-availability clusters?

Why do I have to access the cluster via the high-availability cluster IP?

How long does it take to coordinate the switchover of high-availability clusters?

How do I simultaneously shut down the active server and passive server in a high- availability cluster?

How can I repair a degraded storage space in a high-availability cluster?

Frequently asked questions about Synology High Availability cluster

Software specs

Refer to the Synology High Availability software specifications for DSM 7.0 and DSM 6.2 to

learn more about the package's features, components, and limitations.

Other resources

For more step-by-step tutorials and visual information, feel free to also check out Synology's YouTube channel. There, you can find related videos by searching for "Synology High

Availability".

You can also find more FAQs, tutorials, admin guides, brochures, technical specifications, user

guides, whitepapers, and more for Synology High Availability in Synology Knowledge Center.

Learn more

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