Qdisk

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 Alteeve Wiki :: Qdisk

A Quorum disk, known as a qdisk, in RHCS is a special, small partition used on SAN storage to enhance quorum. It generally carries enough votes to allow even a single node to take quorum during a cluster partition. It does this by using configured heuristics, that is custom tests, to decided which which node or partition is best suited for providing clustered services during a cluster reconfiguration. These heuristics can be simple, like testing which partition has access to a given router, or they can be as complex as the administrator wishes using custom scripts.

Quorum disks are limited to cluster with no more than 16 nodes. This limitation is due to inherent storage latency with larger clusters.

Red Hat's Rob Kenna has a fantastic article on qdisk. It is somewhat dated, but is still very much worth reading.

You can learn more about quorum disk below:

 

Any questions, feedback, advice, complaints or meanderings are welcome.
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