Frequently Asked Question

It is always recommended to create a high-availability (HA) cluster with two identical Synology NAS servers. However, it is also possible to create a hybrid HA cluster using two similar Synology NAS servers as a temporary alternative before you acquire two identical Synology NAS servers. This article will cover the limitations of hybrid HA cluster.

Synology NAS servers supporting hybrid HA clusters:

Model Combinations	DSM Version Tested
DS412+, DS415+	DSM 5.2, DSM 6.0
DS415+, DS916+	DSM 6.0.1
DS713+, DS716+	DSM 5.2, DSM 6.0
DS1512+, DS1513+	DSM 5.2, DSM 6.0
DS1512+, DS1515+	DSM 5.2, DSM 6.0
DS1513+, DS1515+	DSM 5.2, DSM 6.0
DS1812+, DS1813+	DSM 5.2, DSM 6.0
DS1812+, DS1815+	DSM 5.2, DSM 6.0
DS1813+, DS1815+	DSM 5.2, DSM 6.0
DS2413+, DS2415+	DSM 5.2, DSM 6.0
DS3612xs, DS3615xs	DSM 5.2, DSM 6.0
RS812(RP)+, RS814(RP)+	DSM 5.2, DSM 6.0
RS812(RP)+, RS815(RP)+	DSM 5.2, DSM 6.0
RS814(RP)+, RS815(RP)+	DSM 5.2, DSM 6.0
RS2414(RP)+, RS2416(RP)+	DSM 5.2, DSM 6.0

Requirements:

• To ensure the stability of the HA cluster, it is strongly recommended not to consume resources that exceed the specifications of both the active and passive servers.
• The number of drive bays and installed drives must be identical in both the active and passive servers.
• If a Synology Expansion Unit is connected to the active server, the drives and volume allocations in the passive server and its Expansion Unit must be identical to ensure normal failover or switchover.
• The number of LAN ports in use must be identical in both the active and passive servers.

Functions available for hybrid HA clusters:

• High Availability Manager
• File Services
  • Windows File Service
  • Mac File Service
  • NFS File Service
  • FTP Service
• iSCSI LUN/Target

Package limitations:

• Snapshot Replication is not supported if any server in the hybrid HA cluster is any of the following models:
  • DS412+, DS713+, DS1513+, DS1813+, DS2413+, RS814+, RS814RP+, RS2414+, RS2414RP+
• Docker DSM is not supported if any server in the hybrid HA cluster is any of the following models:
  • DS412+, DS713+, DS1513+, DS1813+, DS2413+, RS814+, RS814RP+, RS2414+, RS2414RP+
• Surveillance Station: If the service is switched to the server that has a lower maximum camera capacity, the IP cameras that exceed the limit will be stopped.

Other limitations:

• If a hybrid HA cluster is created using two Synology servers with different specifications, such as CPU frequency, RAM capacity, or maximum connections/shared folders supported, you may experience performance issues if the system service is switched to the server with the slower configuration. In addition, you may not be able to create or adjust any system configurations that exceed the specification of the switched server.
• After a hybrid HA cluster switchover or failover, where Btrfs creation is supported only by the active server and not by the passive server, you can still use the existing Btrfs volumes, however, no more Btrfs volumes can be created.