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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6809) Compressed Commit Log
Date Wed, 20 Aug 2014 05:42:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14103417#comment-14103417
] 

Benedict commented on CASSANDRA-6809:
-------------------------------------

That said, if we have a separate thread per disk, we can have it allocate its next file _after_
its sync completes, thereby saving this cost most of the time too but avoiding any asynchronicity
complexity

> 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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