[jira] Commented: (HBASE-3499) Users upgrading to 0.90.0 need to have their .META. table updated with the right MEMSTORE_SIZE

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    [ https://issues.apache.org/jira/browse/HBASE-3499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12989774#comment-12989774 ] 

stack commented on HBASE-3499:
------------------------------

I added migration notes for 0.90.x over here: http://wiki.apache.org/hadoop/Hbase/HowToMigrate#90

> Users upgrading to 0.90.0 need to have their .META. table updated with the right MEMSTORE_SIZE
> ----------------------------------------------------------------------------------------------
>
>                 Key: HBASE-3499
>                 URL: https://issues.apache.org/jira/browse/HBASE-3499
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.90.0
>            Reporter: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.90.1
>
>
> With Jack Levin, we were able to figure that users that are upgrading from a 0.20.x era cluster have their .META. schema set with a 16KB MEMSTORE_SIZE. This was done in order to minimize lost meta rows when append wasn't available but even if we changed it in HTD, we also have to make sure all users upgrading to 0.90 have it changed too.
> In Jack's case, he ended up with 2143 storefiles in .META. during a cold start, slowing everything down. He reported a few times in the past that his .META. was always extremely busy.
> We should be able to do it as a one-off thing in HMaster when opening .META. (an update in place).

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