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https://issues.apache.org/jira/browse/HBASE-5778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13527669#comment-13527669
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stack commented on HBASE-5778:
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reopen may not be too bad. You have to explain the difference between a reopen
and a getReader somewhere... as is there is none. I don't think it would take
much to explain why you'd reopen (would 'reset' be a better name as in
'resetting the reader'... as to what it does reseting is implementation
specific... If it is a compressed WAL, then we'd reopen the file... if not
compressed, the reset is a noop -- right?)?
ReplicationHLogReader does not implement WAL HLog.Reader interface. Should it?
This javadoc is on the wrong method:
+ * if a positionToSkipTo was specified, this method will take care of
seeking there
I think this patch is almost there.
> Turn on WAL compression by default
> ----------------------------------
>
> Key: HBASE-5778
> URL: https://issues.apache.org/jira/browse/HBASE-5778
> Project: HBase
> Issue Type: Improvement
> Reporter: Jean-Daniel Cryans
> Assignee: Jean-Daniel Cryans
> Priority: Blocker
> Fix For: 0.96.0
>
> Attachments: 5778.addendum, 5778-addendum.txt, HBASE-5778-0.94.patch,
> HBASE-5778-0.94-v2.patch, HBASE-5778-0.94-v3.patch, HBASE-5778-0.94-v4.patch,
> HBASE-5778.patch
>
>
> I ran some tests to verify if WAL compression should be turned on by default.
> For a use case where it's not very useful (values two order of magnitude
> bigger than the keys), the insert time wasn't different and the CPU usage 15%
> higher (150% CPU usage VS 130% when not compressing the WAL).
> When values are smaller than the keys, I saw a 38% improvement for the insert
> run time and CPU usage was 33% higher (600% CPU usage VS 450%). I'm not sure
> WAL compression accounts for all the additional CPU usage, it might just be
> that we're able to insert faster and we spend more time in the MemStore per
> second (because our MemStores are bad when they contain tens of thousands of
> values).
> Those are two extremes, but it shows that for the price of some CPU we can
> save a lot. My machines have 2 quads with HT, so I still had a lot of idle
> CPUs.
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