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 RAID Group, volume, 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.
- 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.
- Network Settings: Both servers of the high-availability cluster must be assigned static IP addresses. Please ensure that your Synology servers are both configured with static rather than DHCP IP addresses. In addition, ensure that the IP addresses of both servers are accessible and belong to the same subnet; otherwise errors might occur when initiating a switchover to the passive server.
- 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.
- PPPoE Unsupported: Synology High Availability does not support PPPoE. Please ensure that PPPoE is switched off before creating a high-availability cluster.
- Link Aggregation Unsupported: Synology High Availability does not support link aggregation. Please ensure that link aggregation is switched off before creating a high-availability cluster.
- Wi-Fi Unsupported: Synology High Availability does not support Wi-Fi. Please ensure that Wi-Fi is switched off before creating a high-availability cluster.
- VLAN Unsupported: Synology High Availability does not support VLAN. Please ensure that VLAN is switched off before creating a high-availability cluster.
Notes: Telnet and SSH functions will be automatically enabled once the high-availability cluster is created.
Storage Manager Limitations
Once a high-availability cluster has been created, certain options in Storage Manager will be unavailable.
- Available Options: The following options are still available when a high-availability cluster exists:
- Expand RAID Groups by adding or replacing hard disks (only for RAID Groups for multiple volumes or iSCSI LUNs).
- Create, delete, or repair volumes and iSCSI LUNs.
- Change iSCSI LUN (File-Level) size and location.
- Change iSCSI LUN target.
- Unavailable Options: The following options cannot be performed when a high-availability cluster exists:
- Edit or expand volume and iSCSI LUN (Block-Level) size.
- Change RAID types.
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 new RAID Groups 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.