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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-7994) Commit logs on the fly compression
Date Tue, 30 Sep 2014 19:24:34 GMT


Jonathan Ellis commented on CASSANDRA-7994:

Marking duplicate to link the two.  Leaving both open until we decide which approach to go

> Commit logs on the fly compression 
> -----------------------------------
>                 Key: CASSANDRA-7994
>                 URL:
>             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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