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From "stack (Assigned) (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (HBASE-5397) [book] zookeeper quorum mistake
Date Tue, 14 Feb 2012 18:50:00 GMT

     [ https://issues.apache.org/jira/browse/HBASE-5397?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

stack reassigned HBASE-5397:

    Assignee: Doug Meil

Can you do this Doug?
> [book] zookeeper quorum mistake
> -------------------------------
>                 Key: HBASE-5397
>                 URL: https://issues.apache.org/jira/browse/HBASE-5397
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Andre Medeiros
>            Assignee: Doug Meil
>            Priority: Minor
> In Chapter 2, section 2.5 "ZooKeeper" under "How many ZooKeepers should I run?" there
is the sentence
> *There can be no quorum if the number of members is an even number.*
> This is not true. In ZooKeeper, an even number of peers is supported, but it is normally
not used because an even sized ensemble requires, proportionally, more peers to form a quorum
than an odd sized ensemble requires. For example, an ensemble with 4 peers requires 3 to form
a quorum, while an ensemble with 5 also requires 3 to form a quorum. Thus, an ensemble of
5 allows 2 peers to fail, and thus is more fault tolerant than the ensemble of 4, which allows
only 1 down peer.

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