ZX Series NAS system failover technologies explained. The team that maintains the failover technologies has been building clustered storage for over 20 years so it is a seasoned team. Expect the Scale Logic ZX to be class-leading among peers.
- SAS drives - dual ports on the storage devices themselves including flash devices
- Dual Expander JBODs - dual expander backplanes allow SAS bus failover inside all chassis
- Dual SAS Cables - MPIO enabled in the NAS allows 2 physical paths to each storage device
- Dual nodes in HA mode - 2 identical NAS servers with one node acting as a hot spare for the storage pool operations
- Cluster Resource Manager - uses STONITH ("Shoot The Other Node In The Head" or "Shoot The Offending Node In The Head"), a technique for fencing in computer clusters that prevents cluster split-brain and removes potential cluster instability
- Network Bonds - bonded network interfaces allow ethernet cable failures
- Network-based heartbeat and ping - used by the Cluster Resource Manager to ensure the health of nodes and promote or demote nodes by power cycling etc.
- Multi-Modifier protection - Base code developed by Lawrence Livermore Labs and funded by Intel - deep protection to prevent a pool to be imported by 2 nodes at the same time "split-brain" - https://openzfs.org/w/
images/d/d9/05-MMP-openzfs- 2017.4.pdf - Critical system error response policy - prevents cluster instability and triggers failover in case of unexpected hardware malfunctions.
- Cluster watchdog - monitors volume availability and reboots the node to trigger pool failover in case of inaccessibility
- IPMI hardware watchdog - monitors to guarantee a clean reboot or force a hung reboot for clean failover