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From "Aleksey Yeschenko (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-7994) Commit logs on the fly compression
Date Wed, 25 Mar 2015 08:36:53 GMT


Aleksey Yeschenko commented on CASSANDRA-7994:

Since changing something as major as that on 2.0, or even 2.1 at the time was a no go, we
went with CASSANDRA-6809 on trunk option.

I believe that some of the points raised by Oleg have been addressed there, though not all.

I suggest we create separate follow up tickets for the remained of them (like we did with
CASSANDRA-8634), to be addressed in either 3.0 or 3.1, if you can find some time for that,

Will be closing this one as a duplicate for now.

> Commit logs on the fly compression 
> -----------------------------------
>                 Key: CASSANDRA-7994
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Oleg Anastasyev
>            Assignee: 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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