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From "Karl Mueller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8177) sequential repair is much more expensive than parallel repair
Date Sat, 25 Oct 2014 00:03:07 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14183757#comment-14183757
] 

Karl Mueller commented on CASSANDRA-8177:
-----------------------------------------

"Sequential repair is meant to be used where validation compaction on all replica will impact
on overall cluster performance. If parallel repair does the job, then stick with it is fine."

Why on earth is serial repair the default then??  parallel is a better default!

> sequential repair is much more expensive than parallel repair
> -------------------------------------------------------------
>
>                 Key: CASSANDRA-8177
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8177
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sean Bridges
>            Assignee: Yuki Morishita
>         Attachments: cassc-week.png, iostats.png
>
>
> This is with 2.0.10
> The attached graph shows io read/write throughput (as measured with iostat) when doing
repairs.
> The large hump on the left is a sequential repair of one node.  The two much smaller
peaks on the right are parallel repairs.
> This is a 3 node cluster using vnodes (I know vnodes on small clusters isn't recommended).
 Cassandra reports load of 40 gigs.
> We noticed a similar problem with a larger cluster.



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