QS Introduction SharedNothing - HAC documentation hub

QS Introduction SharedNothing

A shared-nothing cluster consists of two nodes, each with their own locally accessible ZFS storage pool residing on non shared storage:

flowchart TD
    SNa("Node A")<-->|SAS/FC etc.|SNSa
    SNb("Node B")<-->|SAS/FC etc.|SNSb

Data is replicated between nodes by an HA synchronisation process. Replication is always done from the active to the passive node, where the active node is the one serving out the pool to clients:

flowchart LR
    SNa("Node A (active)<br />Pool-A")-->|HA Synchronisation|SNb
    SNb("Node B (passive)<br />Pool-A")

Should a failover occur then synchronisation is effectively reversed:

flowchart RL
    SNa("Node B (active)<br />Pool-A")-->|HA Synchronisation|SNb
    SNb("Node A (passive)<br />Pool-A")

Before creating pools for shared nothing clusters

  1. To be eligible for clustering the storage pools must have the same name on each node in the cluster

  2. It is strongly recommended the pools are of equal size, otherwise the smaller of the two runs the risk of depleting all available space during synchronization