Synology High Availability Technical Specifications

Synology High Availability

Features

Real-time data replication between the active and passive servers to maintain data consistency and maximize service availability
Automatic failover to minimize system interruption resulting from service failures or hardware unavailability
Unified and friendly user interface to easily manage and monitor the high-availability cluster
Easy-to-navigate dashboard to closely monitor CPU, memory, and drive utilization on both servers
Intuitive and easy-to-follow troubleshooting process

Specifications

System requirements:
- A high-availability cluster requires two identical Synology NAS devices (Applied models)
- Two Synology NAS devices must have identical system configurations such as DSM and SHA versions, drive numbers and capacities, system partition and slot placement (Learn more)
Functionality:
- Supports updating DSM and package versions for both servers
- Allows shutting down and restarting either the entire high-availability cluster or individual hosts
- Supports setting up a quorum server to minimize the occurrence of split-brain errors
- Manual switchover to periodically test and ensure the functioning of high-availability
- Automatic failover ensures system availability when:
  - SMB, iSCSI, AFP, FTP, NFS, Synology Directory Server, or web services are down
  - Storage space fails
  - The high-availability cluster loses network connection with clients
  - The active server becomes unavailable
Storage:
- Supports RAID 0, RAID 1, RAID 5, RAID 6, RAID 10, RAID F1, JBOD and Basic
- Maximum total number of volumes and LUNs per high-availability cluster: 64
- The maximum total capacity for volumes and LUNs per high-availability cluster varies based on when the servers' system partitions are created:
  - DSM 7.1 or above - 1 PB (Learn more)
  - Before DSM 7.1 - 400 TB
- Allows creation of WriteOnce (WORM) or encrypted volumes, requiring support from both servers
Network:
- A high-availability cluster requires at least one static IP address for external communication with client devices
- The active and passive servers should set the same Link Aggregation mode based on network configuration (Learn more)
Power Supply:
- Supports SNMP UPS, USB UPS, Synology UPS servers

Limitations

Functions:
- HDD hibernation is not supported in a high-availability cluster
- Passive server is not available for user login as all operations are processed on the active server
Packages:
- A high-availability cluster does not support the following packages:
  - PetaSpace
  - Migration Assistant
- The cluster feature for Virtual Machine Manager is not supported
- The cluster feature for Synology MailPlus Server is not supported
- Cannot shut down or restart a high-availability cluster via Synology Central Management System (CMS)
- Synology Directory Server should be configured after cluster creation. Refer to the User Guide if already installed
Storage:
- SHR-formatted volumes and M.2 volumes are not supported
- Drive positions within the active and passive servers cannot be changed post-creation
- Switchover/failover for USB devices is not supported as services or applications provided by USB devices may not work properly after switchover/failover
- USB devices are only accessible when connected to the active server
Network:
- The servers cannot connect to the network via IPv6, PPPoE, or Wi-Fi
- The Heartbeat interface does not support VLAN ID
- A Heartbeat connection requires low latency with response time less than 1 ms
- The Link Aggregation mode cannot be modified post-creation
Performance:
- Allocating system resources to create and maintain a high-availability cluster can impact random write performance by up to 15% (Learn more)
Hybrid high-availability cluster:
- A hybrid high-availability cluster can be created with two different Synology NAS devices in some scenarios, such as when one of the servers is undergoing repairs or replacement, but it is generally recommended to use two identical Synology NAS devices for better performance (Learn more)
- Hybrid Share folders cannot be mounted on a high-availability cluster created with two different Synology NAS models (Release notes)
- For 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
- Virtual Machine Manager is not supported
- M.2 SSD caching is not supported in a hybrid high-availability cluster with mixed built-in M.2 slot types (e.g., DS1621+ and DS1618+)