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Knowledge Center

Synology High Availability

High Availability refers to a server layout solution designed to reduce interruptions of services caused by server malfunctions. Synology High Availability uses two 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." 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 NAS servers to create a high-availability cluster. One server acts as the "active server " while the other acts as the "passive server." Once the high-availability cluster is created, the system will continuously replicate data from the active server to the passive server, so that all files on the active server will exist in duplicate on the passive server. If 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. With this implementation in place, the high-availability cluster can continue to provide services normally and thus minimize downtime.
  • Active Server: The active server manages the provision of all services. If errors occur on the active server, you or the system can transfer the services on the active server to the passive server via a switchover/auto-failover, and in this process, the active server becomes the passive server.
  • Passive Server: The passive server remains in standby mode under normal conditions. Data on the active server is continuously being replicated to the passive server. If the active server can no longer provide services, you or the system can initiate a switchover/auto-failover to allow the passive server to take over services from the active server.
  • Heartbeat Connection: The active and passive servers of a high-availability cluster are linked by a dedicated, private network connection referred to as the "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 if a switchover is necessary.
  • Main Storage Volume in a High-Availability Cluster: The volume on the active server will become the main storage of the high-availability cluster. Data is replicated to the passive server's storage volume through the Heartbeat connection.
  • Spare Storage Volume in a High-Availability Cluster: The volume on the passive server will become the high-availability cluster's spare storage. 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 a single 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 Address: Although each server in the high-availability cluster has its own IP address, the high-availability cluster can also generate common IP addresses. You can use these common IP address to access any DSM services, regardless of which Synology NAS server is acting as the active server. Moreover, you will not have to change to another IP address to access services whenever a switchover/auto-failover is performed.