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From "Sean Bridges (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8177) sequential repair is much more expensive than parallel repair
Date Thu, 23 Oct 2014 23:16:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14182157#comment-14182157
] 

Sean Bridges commented on CASSANDRA-8177:
-----------------------------------------

We can't easily upgrade to 2.1.

I don't think this issue is a dupe of CASSANDRA-5220. Looking at the graphs, I think something
is quite wrong with sequential or parallel  repair.  With a 3 node cluster, using sequential
shouldn't cause repairs to take 13 times as long, and use a lot more io.


> 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
>         Attachments: 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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