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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8344) Improve the assignment when node failures happen to choose the secondary RS as the new primary RS
Date Thu, 23 May 2013 21:09:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13665675#comment-13665675
] 

Devaraj Das commented on HBASE-8344:
------------------------------------

bq. What's happens if we lose 2 nodes out of the ensemble of 3? Will we have the 3 region
sets on the last one remaining?

Nope. The last one will only be the current "owner" of the region and have one copy of the
region files' blocks. On node failures the favored-nodes mapping is not updated (a comment
is there in the code on this). The balancer, when it runs, would figure the best favored nodes
for the regions. When the balancer figures the best nodes, the RegionServers in question would
be made aware of the new mapping... Until the balancer runs, any RegionServer would continue
to use the old favored nodes mapping for HDFS file creations and the NameNode in turn will
allocate replica locations that are "close" (same rack for example) to the favored-nodes the
RegionServer is passing as hints. 
                
> Improve the assignment when node failures happen to choose the secondary RS as the new
primary RS
> -------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-8344
>                 URL: https://issues.apache.org/jira/browse/HBASE-8344
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Devaraj Das
>            Assignee: Devaraj Das
>            Priority: Critical
>             Fix For: 0.95.2
>
>         Attachments: hbase-8344-1.txt, hbase-8344-2.1.txt
>
>


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