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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4344) Persist memstoreTS to disk
Date Fri, 23 Sep 2011 03:47:26 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13113141#comment-13113141
] 

Lars Hofhansl commented on HBASE-4344:
--------------------------------------

I ran TestSplitTransaction again with the patch but the various high volume LOG.debugs removed.
It back to the original speed.

So IMHO, we cannot ship this with all the LOG.debug statements, because it'd be so slow that
nobody could switch on debug logging to diagnose a production problem.


> Persist memstoreTS to disk
> --------------------------
>
>                 Key: HBASE-4344
>                 URL: https://issues.apache.org/jira/browse/HBASE-4344
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Amitanand Aiyer
>            Assignee: Amitanand Aiyer
>             Fix For: 0.89.20100924
>
>         Attachments: 4344-v2.txt, 4344-v4.txt, 4344-v5.txt, 4344-v6.txt, 4344-v7.txt,
patch-2
>
>
> Atomicity can be achieved in two ways -- (i) by using  a multiversion concurrency system
(MVCC), or (ii) by ensuring that "new" writes do not complete, until the "old" reads complete.
> Currently, Memstore uses something along the lines of MVCC (called RWCC for read-write-consistency-control).
But, this mechanism is not incorporated for the key-values written to the disk, as they do
not include the memstore TS.
> Let us make the two approaches be similar, by persisting the memstoreTS along with the
key-value when it is written to the disk.

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