Without a witness, an even-numbered cluster is at risk of split-brain. If a node loses contact with the cluster it becomes isolated, operating independently, and its data becomes inconsistent with the rest of the cluster. When this node is eventually reintroduced to the cluster, these inconsistencies may result in data corruption and potentially even data loss.
The SvSAN witness prevents split-brain scenarios from occurring by regularly checking the state of each node in an SvSAN cluster. The only data passing between the witness and the SvSAN nodes is the ‘heartbeat’ – the witness is not in the data path. This allows it to tolerate significant latency and low bandwidth, and can therefore be located great distances from the clusters it provides quorum service for, even if they are in remote, harsh environments.
These attributes make the witness an ideal fit for organizations with many locations where local highly available storage is a requirement at each site. Whether it’s retail chains with thousands of stores, energy firms with scattered wind farms and facilities in remote locations, or manufacturing plants around the world, the SvSAN witness provides simple, resilient and cost-effective protection for two node clusters at every one.