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From "Gabriel Ki (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2427) Heuristic or hard cap to prevent fragmented commit logs from bringing down the server
Date Mon, 13 Jun 2011 20:53:51 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13048753#comment-13048753
] 

Gabriel Ki commented on CASSANDRA-2427:
---------------------------------------

Are you planing on changing the value once Cassandra is running?

I guess my question is, although one shouldn't do this manually are there anything else we
could force a flush after memtable_flush_after_mins is removed?  The memtable_flush_after_mins
and memtable through put settings didn't work for me with 0.7.6-2.

It will only flush one CF at a time, and that will be the ones with the oldest segment.

The problem is I have a hot CF and the data is coming in uniformly to all keys.  The only
thing I could do to prevent commit log disk full at this moment is to do a rotation restart
of the nodes. 


> Heuristic or hard cap to prevent fragmented commit logs from bringing down the server
> -------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-2427
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2427
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Benjamin Coverston
>            Assignee: Patricio Echague
>              Labels: commitlog, hardening
>             Fix For: 1.0
>
>         Attachments: CASSANDRA-2427-trunk.txt
>
>
> Widely divergent write rates on column families can cause the commit log segments to
fragment. In some cases we have seen the commit log partition overrun.
> One solution here would be to create a heuristic for segment fragmentation to trigger
a flush (commit log segments/memtable) or simply track the free disk space and force a global
flush when the disk gets to 80% capacity.

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