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Date: Thu, 3 May 2012 20:10:48 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-5930) Periodically flush the Memstore?
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    [ https://issues.apache.org/jira/browse/HBASE-5930?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13267765#comment-13267765 ] 

Lars Hofhansl commented on HBASE-5930:
--------------------------------------

What should trigger the flush is an interesting discussion in itself. Should we flush:
* after N timeunits of write inactivity, or
* when the last flush happened more than N TUs ago

The former would avoid smaller storefiles, the latter would put a limit on how stale an entry in the memstore can be.

                
> Periodically flush the Memstore?
> --------------------------------
>
>                 Key: HBASE-5930
>                 URL: https://issues.apache.org/jira/browse/HBASE-5930
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Lars Hofhansl
>            Priority: Minor
>
> A colleague of mine ran into an interesting issue.
> He inserted some data with the WAL disabled, which happened to fit in the aggregate Memstores memory.
> Two weeks later he a had problem with the HDFS cluster, which caused the region servers to abort. He found that his data was lost. Looking at the log we found that the Memstores were not flushed at all during these two weeks.
> Should we have an option to flush memstores periodically. There are obvious downsides to this, like many small storefiles, etc.

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