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From "Jason Brown (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-6809) Compressed Commit Log
Date Wed, 20 Aug 2014 08:44:26 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14103626#comment-14103626
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Jason Brown edited comment on CASSANDRA-6809 at 8/20/14 8:42 AM:
-----------------------------------------------------------------

If we did try an async flush of the buffers in a sync thread, I think it would be instructive
to actually measure that it is demonstratively beneficial, rather than assuming that it is.
I'm not immediately sure how to measure that, but it's near 2am and coffee time doesn't begin
for several more hours.


was (Author: jasobrown):
If we did try an async flush of the buffers in a sync thread, I think it would be instructive
to actually measure that it is demonstratively beneficial, rather than assuming that it is.

> Compressed Commit Log
> ---------------------
>
>                 Key: CASSANDRA-6809
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6809
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Benedict
>            Assignee: Branimir Lambov
>            Priority: Minor
>              Labels: performance
>             Fix For: 3.0
>
>
> It seems an unnecessary oversight that we don't compress the commit log. Doing so should
improve throughput, but some care will need to be taken to ensure we use as much of a segment
as possible. I propose decoupling the writing of the records from the segments. Basically
write into a (queue of) DirectByteBuffer, and have the sync thread compress, say, ~64K chunks
every X MB written to the CL (where X is ordinarily CLS size), and then pack as many of the
compressed chunks into a CLS as possible.



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