Limitations and System Requirements
Implementation of Synology High Availability requires two identical Synology servers to act as active and passive servers. Before the two servers are combined into a high-availability cluster, the Synology High Availability Wizard will check for the following hardware and software limitations to ensure that a high-availability cluster can be created.
System Requirements
Please note the following guidelines regarding software and hardware:
- Synology Server: Both the active and passives servers must be identical models and support Synology High Availability.
- DSM Version: The same version of DSM must be installed on both the active and passive servers.
- Package Version: The same version of Synology High Availability must be installed on both Synology servers.
Volume and Hard Disk
Please note the following guidelines regarding storage spaces (e.g. volumes, Disk Groups, RAID Groups, etc.) and hard disk management.
- Storage Volume: In order to accommodate data replication, the storage capacity of the passive server must be equal to or larger than the capacity of the active server. It is strongly advised that the storage capacity of both servers be completely identical to reduce the chances of inconsistencies.
- Number of Disks: Both the active and passive servers must have the same quantity of hard disks. In addition, hard disk numbering and position must correspond in both servers. Please note external devices like USB hard drives will not be included when counting the number of disks.
- SHR Format Unsupported: SHR format volumes are not supported. Please ensure that the Synology server which will act as the active server does not contain SHR volumes.
Network Environment
Please note the following guidelines regarding network settings when attempting to form a high-availability cluster.
- Network Settings: Both servers must have static IP addresses belonging to the same subnet.
- Number of LAN Ports: Both servers must have the same number of LAN ports. If your Synology NAS is equipped with additional network card interfaces, these network cards also count as additional LAN ports.
- Connection Restrictions: The servers cannot connect to the network via a proxy server, DHCP, IPv6, PPPoE, and Wi-Fi. Please ensure that these functions are disabled before attempting to form a high-availability cluster.
- No DHCP service: The servers cannot use the built-in DHCP server options when combined into a cluster.
Note:
- SSH will be enabled automatically once the high-availability cluster is created.
Storage Manager Limitations
Once a high-availability cluster has been formed, the option to change RAID type will no longer be available in Storage Manager. However the following options will be available:
- Expand storage spaces (e.g. volumes, Block-Level iSCSI LUNs, Disk Groups, RAID Groups, etc).
- Create, delete, or repair volumes and iSCSI LUNs.
- Change iSCSI LUN (File-Level) size and location.
- Change iSCSI LUN target.
Please note, SSD read-write cache is not supported when the servers are combined into a cluster.
Package and Software Limitations
Please see the package and software related limitations below:
- Once the high-availability cluster had been formed, the following packages will not be supported:
- Zarafa
- Symform
- CIFS Scale-out Cluster feature in CMS
- We do not recommended providing AFP service to transfer many files smaller than 1MB with the high-availability cluster.
Adding Expansion Units
Once a high-availability cluster has been created, expansion units can be added to your existing high-availability cluster configuration in order to expand storage capacity. As with other hardware requirements, identical expansion units are required for both the active and passive servers. To avoid inconsistency errors, please be careful to follow the instructions below when adding any expansion units.
To add expansion units:
- Only add identical expansion units and hard disks to the active and passive servers. As stated above, the hardware of both the active and passive servers must be identical, including hardware model, and hard disk size and position.
- Make sure to delete all existing data and volumes on the hard disks in the expansion units.
- Connect expansion units to the active and passive servers when both servers are powered on and running.
- Create a new storage space (e.g. volumes, Disk Groups, RAID Groups, etc.) on the expansion unit before powering off either of the servers.
Notes:
For basic information regarding expansion unit installation, please remember to see the user's guide for your expansion unit.