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https://issues.apache.org/jira/browse/HBASE-5930?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13561302#comment-13561302
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Enis Soztutar commented on HBASE-5930:
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bq. I would like to pick this up again and add a flag to Mutation to indicate
deferred WAL sync. If HRegion receives a batch of Mutation of which at least
one is not marked as deferred the log is sync'ed. Otherwise it is deferred.
I like the idea of having a deferred flush at the Put level. Now the weird
thing is that it is per table, not per column family. I guess we can have
per-table/per-cf or per batch deferred flush setting.
With this, maybe we will no longer need skipWAL if we can prove that deferred
flush is as fast as skip WAL. Most of the time, we actually do not want to skip
WAL, we just want a deferred flush.
bq. I decided to separate the issue of having the feature on asynchronous write
to WAL from the periodic flush
+1 on doing separating the two.
> Periodically flush the Memstore?
> --------------------------------
>
> Key: HBASE-5930
> URL: https://issues.apache.org/jira/browse/HBASE-5930
> Project: HBase
> Issue Type: Improvement
> Reporter: Lars Hofhansl
> Assignee: Devaraj Das
> Priority: Minor
> Fix For: 0.96.0
>
> Attachments: 5930-wip.patch
>
>
> 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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