Synology High Availability
High Availability refers to a server layout solution designed to reduce interruptions of services caused by server malfunctions. High Availability uses multiple servers to form a "high-availability cluster" in which one server assumes the role of "active server" and another server acts as a standby "passive server." In order to implement and create a high-availability cluster, you need two compatible Synology servers.
A high-availability cluster makes use of the following components and concepts:
- Concept: Implementation of Synology High Availability requires two Synology servers to create a high-availability cluster. One server acts as "active server" and the other acts as "passive server." Once the high-availability cluster is created, data is continuously replicated from the active server to the passive server. All files on the active server will exist in duplicate on the passive server. In the event the active server malfunctions, the passive server will be ready to take over all services with a complete mirrored copy of the data on the active server. Thus, the high-availability cluster will continue providing services normally, minimizing server downtime. For more details regarding switchover, please refer to Switchover
- Active server: The active server manages the provision of all services. In the event errors occur on the active server, you or the system can initiate a switchover to the passive server. In this case, the provision of services is transferred to the passive server, at which point the active server becomes the passive server.
- Passive server: Under normal conditions, the passive server remains in standby mode. Data on the active server is continuously replicated to the passive server. In the event the active server cannot provide services, you or the system can initiate a switchover to the passive server.
- Heartbeat connection: The active and passive servers of a high-availability cluster are linked by a dedicated, private network connection referred to as "Heartbeat connection." Once the high-availability cluster has been created, the Heartbeat connection facilitates data synchronization and replication between the active and passive servers. If contact between the servers is lost for a given amount of time, the system will determine a switchover is necessary.
- High-availability cluster main storage volume: The storage volume of the active server will become the main storage volume of the high-availability cluster. Data is replicated to the passive server's storage volume through the Heartbeat connection.
- High-availability cluster spare storage volume: The storage volume on the passive server will become the high-availability cluster's spare storage volume. Data is continuously replicated from the active server storage volume to the passive storage volume via the Heartbeat connection. This ensures the consistency of file content when a switchover occurs.
- High-availability cluster server name: Servers in the high-availability cluster will share one server name. In the network, you can connect using this server name, and services will be provided by the active server.
- High-availability cluster IP: As the active and passive servers in the high-availability cluster each has its own IP address, to avoid having to change to another IP address when a switchover is performed, the high-availability cluster will generate common IP addresses for access. To access any DSM services, regardless of which Synology server is acting as the active server, you can connect through these IP addresses.
High Availability Features
This section describes the limitation and requirements of high-availability cluster. Make sure to read this section before you start using Synology High Availability.
This wizard helps create and configure a high-availability cluster.
Displays basic information about the high-availability cluster and member servers. This section also provides tools to create and manage the high-availability cluster
View information and edit settings related to the high-availability cluster's IP address; Change the name or IP address of the high-availability cluster's server.
View services which can be monitored; Indicate whether services should be transferred from the active server to the passive server, and the two servers roles exchanged, if monitored services malfunction.
Displays the status of all usable volumes and iSCSI LUNs (Block-Level) on the high-availability cluster. When a volume or iSCSI LUN crashes or becomes degraded, you can repair it from this page.
View the statuses of the disks in the active and passive servers. If you wish to replace disks, please use this page to ascertain the corresponding disk numbers in the active and passive servers. It is strongly advised that disks of identical storage volume be used for the same disk number on both the active and passive servers.
This section provides an explanation of performing a switchover of services from the active server to the passive server.
This section guides you through the process of shutting down, removing, or resetting a high-availability cluster.
This section guides you through the process of fixing a split-brain error.