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From Rob Coli <>
Subject Re: Node-tool drain on Cassandra 1.0
Date Wed, 12 Sep 2012 23:16:41 GMT
On Sun, Sep 9, 2012 at 12:01 PM, Robin Verlangen <> wrote:
> Deleting the commitlog files is harmless. It's just a tool that tries to
> keep Cassandra more in-sync with the other nodes. A standard repair will fix
> all problems that a commitlog replay might do too.

This is not really true.. imagine a RF=2 cluster.

1) take a replica node down
2) write at CL.ONE to another replica node
3) replication fails to other replica due to it being down, hint is
queued locally, this means both writes are only in memtables/mirrored
in the commitlog
4) don't nodetool flush
5) stop node
6) delete commitlog

You have now lost data, and repair can't fix it, because the data
you've lost has not been written to any other node. This is one of the
edge cases that makes CL.ONE pretty risky if you care about your data
and use a RF under 3.


=Robert Coli
YAHOO - rcoli.palominob
SKYPE - rcoli_palominodb

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