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Date: Tue, 2 Jul 2013 03:56:21 +0000 (UTC)
From: "Dave Latham (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12655665.1372717710440.196642.1372737381436@arcas>
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Subject: [jira] [Commented] (HBASE-8844) Document stop_replication danger
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    [ https://issues.apache.org/jira/browse/HBASE-8844?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13697482#comment-13697482 ] 

Dave Latham commented on HBASE-8844:
------------------------------------

There are some cases where it can affect the master cluster as well.  We actually were bit in the master cluster by having the master go OutOfMemory a couple of weeks after using stop_replication.  We did not lose any data from the master cluster.  Some more details in the thread here:
http://mail-archives.apache.org/mod_mbox/hbase-user/201302.mbox/%3CCAA4mzoky-4G-235_ta41tDNfL1K-RtT0f3Q=XLXF930Wq=y_nw@mail.gmail.com%3E

The main cause if replication is enabled in the configuration but you run stop_replication then the master will stop cleaning out all HLog files from .oldlogs.  (e.g. HBASE-3489)

Now that HBASE-3134 is in I would recommend always using disable_peer rather than stop_replication and treat stop_replication as dangerous.
                
> Document stop_replication danger
> --------------------------------
>
>                 Key: HBASE-8844
>                 URL: https://issues.apache.org/jira/browse/HBASE-8844
>             Project: HBase
>          Issue Type: Task
>          Components: documentation
>            Reporter: Patrick
>            Priority: Minor
>         Attachments: HBASE-8844.patch
>
>
> The first two tutorials for enabling replication that google gives me [1], [2] take very different tones with regard to stop_replication. The HBase docs [1] make it sound fine to start and stop replication as desired. The Cloudera docs [2] say it may cause data loss.
> Which is true? If data loss is possible, are we talking about data loss in the primary cluster, or data loss in the standby cluster (presumably would require reinitializing the sync with a new CopyTable).
> [1] http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/replication/package-summary.html#requirements
> [2] http://www.cloudera.com/content/cloudera-content/cloudera-docs/CDH4/4.2.0/CDH4-Installation-Guide/cdh4ig_topic_20_11.html

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