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From "Patrick Hunt (JIRA)" <j...@apache.org>
Subject [jira] Created: (ZOOKEEPER-546) add "diskless" ensemble support
Date Thu, 08 Oct 2009 16:40:31 GMT
add "diskless" ensemble support

                 Key: ZOOKEEPER-546
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-546
             Project: Zookeeper
          Issue Type: New Feature
          Components: server
            Reporter: Patrick Hunt
             Fix For: 3.3.0

In some cases there is no need to have the ZK data persisted to disk. For example if all you
are doing is group membership and leadership
election the data is totally ephemeral, storing on disk is unnecessary. We've also seen cases
where any non-ephemeral data can be
easily recovered (say configuration data that's generated/read and loaded into zk) and there
is less need to worry about recovery of the
data in the case of catastrophic failure (meaning _all_ replicas are lost, remember, recovery
is automatic if 2n+1 servers and <= n servers
fail, even if > n fail manual recovery is still possible as long as at least 1 replica,
or replica backup can be recovered)

In these cases it makes sense to have a "diskless" zookeeper ensemble. The result should be
improved write performance
an less moving parts (no disk to fail!), simplifiying ops in cases where this can be applied.

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