[jira] [Commented] (CASSANDRA-7994) Commit logs on the fly compression

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14145259#comment-14145259 ] 

Jonathan Ellis commented on CASSANDRA-7994:
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Can you compare your approach to the one in CASSANDRA-6809?

> Commit logs on the fly compression 
> -----------------------------------
>
>                 Key: CASSANDRA-7994
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7994
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Oleg Anastasyev
>         Attachments: CompressedCommitLogs-7994.txt
>
>
> This patch employs lz4 algo to comress commit logs. This could be useful to conserve disk space either archiving commit logs  for a long time or for conserviing iops for use cases with often and large mutations updating the same record.
> The compression is performed on blocks of 64k, for better cross mutation compression. CRC is computed on each 64k block, unlike original code computing it on each individual mutation.
> On one of our real production cluster this saved 2/3 of the space consumed by commit logs. The replay is 20-30% slower for the same number of mutations.
> While doing this, also refactored commit log reading code to CommitLogReader class, which i believe makes code cleaner.



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