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https://issues.apache.org/jira/browse/CASSANDRA-1470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12970103#action_12970103
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Oleg Anastasyev commented on CASSANDRA-1470:
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Guys, may be I misunderstand something, but are we trying to make compaction 
writes faster ? This is background data maintenance process, and I think it is 
not very much important how fast is it. I think most important about it is how 
much it makes normal (read) requests serving slower, keeping valuable 
resources, especially memory, busy. 
Did we measured the impact of compaction on read requests  of  direct IO writes 
compaction vs old normal writes compaction ?



> use direct io for compaction
> ----------------------------
>
>                 Key: CASSANDRA-1470
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1470
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Pavel Yaskevich
>             Fix For: 0.7.1
>
>         Attachments: 1470-v2.txt, 1470.txt, CASSANDRA-1470-for-0.6.patch, 
> CASSANDRA-1470-v10-for-0.7.patch, CASSANDRA-1470-v11-for-0.7.patch, 
> CASSANDRA-1470-v12-0.7.patch, CASSANDRA-1470-v2.patch, 
> CASSANDRA-1470-v3-0.7-with-LastErrorException-support.patch, 
> CASSANDRA-1470-v4-for-0.7.patch, CASSANDRA-1470-v5-for-0.7.patch, 
> CASSANDRA-1470-v6-for-0.7.patch, CASSANDRA-1470-v7-for-0.7.patch, 
> CASSANDRA-1470-v8-for-0.7.patch, CASSANDRA-1470-v9-for-0.7.patch, 
> CASSANDRA-1470.patch, 
> use.DirectIORandomAccessFile.for.commitlog.against.1022235.patch
>
>
> When compaction scans through a group of sstables, it forces the data in the 
> os buffer cache being used for hot reads, which can have a dramatic negative 
> effect on performance.

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