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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-12577) Disable distributed log replay by default
Date Mon, 01 Dec 2014 19:03:13 GMT

     [ https://issues.apache.org/jira/browse/HBASE-12577?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Enis Soztutar updated HBASE-12577:
    Release Note: 
Disabled Distributed Log Replay (DLR) as default WAL/hlog splitting mechanism. 1.0.x releases
will default to Distributed Log Splitting (DLS) system which is the default for 0.98, 0.96
and 0.94 releases. 

DLR improves MTTR (the more regions a server is carrying, the better the improvement. Also,
we can start taking writes during WAL/hlog recovery), but rolling upgrade to HBase-1.0.x from
earlier releases of 0.98 branch (0.98.0,..,0.98.3) can result in data loss. If you are not
doing rolling upgrade, or you are rolling upgrading from a 0.98 greater than or equal to 0.98.4,
you can safely turn on distributed log replay by default. Regular upgrade (as opposed to rolling
upgrade) is not affected. See HBASE-11094 for details. 

See HBASE-7006 to learn more about DLR. You can enable this feature by setting hbase.master.distributed.log.replay
to true in your hbase-site.xml file. 

> Disable distributed log replay by default
> -----------------------------------------
>                 Key: HBASE-12577
>                 URL: https://issues.apache.org/jira/browse/HBASE-12577
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Enis Soztutar
>            Assignee: Jeffrey Zhong
>            Priority: Critical
>             Fix For: 0.99.2
>         Attachments: HBASE-12567.patch, HBASE-12567.patch
> Distributed log replay is an awesome feature, but due of HBASE-11094, the rolling upgrade
story from 0.98 is hard to explain / enforce. 
> The fix for HBASE-11094 only went into 0.98.4, meaning rolling upgrades from 0.98.4-
might lose data during the upgrade. 
> I feel no matter how much documentation / warning we do, we cannot prevent users from
doing rolling upgrades from 0.98.4- to 1.0. And we do not want to inconvenience the user by
requiring a two step rolling upgrade.  
> Thus I think we should disable dist log replay for 1.0, and re-enable it again for 1.1
(if rolling upgrade from 0.98 is not supported). 
> ie. undo: HBASE-10888

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