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Posted to dev@zookeeper.apache.org by "Flavio Junqueira (JIRA)" <ji...@apache.org> on 2012/07/12 00:35:34 UTC
[jira] [Commented] (ZOOKEEPER-1508) Reliable standalone mode
through redundant databases
[ https://issues.apache.org/jira/browse/ZOOKEEPER-1508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13412242#comment-13412242 ]
Flavio Junqueira commented on ZOOKEEPER-1508:
---------------------------------------------
Bill and I have been having discussions offline about this feature. I like it a lot and I think we should do it. One question I have is if this diverges enough from the current project that it warrants a new subproject.
> Reliable standalone mode through redundant databases
> ----------------------------------------------------
>
> Key: ZOOKEEPER-1508
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1508
> Project: ZooKeeper
> Issue Type: New Feature
> Environment: Single server with multiple disks or two node cluster with multiple shared disks
> Reporter: Bill Bridge
>
> Currently ZooKeeper requires 3 servers to provide both reliability and availability. This is fine for large internet scale clusters, but there are lots of two node clusters that could benefit from ZooKeeper. There are also single server use cases where it is highly desirable to have ZooKeeper survive a disk failure, but availability is not as important.
> This feature would allow the configuration of multiple destinations for logs and snapshots. A transaction is committed when a majority of the log writes complete successfully. If one log gets an error on write, then it is taken offline until an administrator brings it online or replaces it with a new destination. ZooKeeper continues to run as long as a quorum of disks can be written.
> High availability can be provided with a two node cluster. When the ZooKeeper node dies, the disks are switched to the surviving node and a new ZooKeeper starts. Faster switch over can be done if there is an observer already running in the new node.
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