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From "Jean-Daniel Cryans (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5778) Turn on WAL compression by default
Date Fri, 14 Dec 2012 23:26:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13532784#comment-13532784
] 

Jean-Daniel Cryans commented on HBASE-5778:
-------------------------------------------

bq. My question becomes: shall we introduce TestWALReplayUncompressed

That makes sense.

bq. Running the patch on Linux I got:

If you change SLEEP_TIME for 1500, does it still fail? If not, that's the IPV6 problem.

bq. Please add annotation for audience and stability.

Thanks, forgot about that.

bq. Please phase the above line so that it is easier to understand.

It works the same way as reader.next, is there anything in particular you think needs more
explanation?
                
> 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-5778-0.94-v5.patch, HBASE-5778-0.94-v6.patch,
HBASE-5778.patch, HBASE-5778-trunk-v6.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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