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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1470) use direct io for compaction
Date Wed, 08 Dec 2010 17:26:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12969385#action_12969385
] 

Pavel Yaskevich commented on CASSANDRA-1470:
--------------------------------------------

Seems that DEFAULT_DIRECT_BUFFER_SIZE = 16kb is the best option here I was playing with it
for some time.

Can you please apply v12 patch and test it on your machine so we can see results you will
get comparing to your previous comment? Would be very helpful... 

Direct I/O writes will be slower than ordinary writes because of data transfer performed directly
to the device without Page Writeback technique which kernel performs. I will work on write
solution for dirty Direct I/O buffers on my side...

> 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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