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From Jonathan Ellis <>
Subject Re: Newbie Question about restarting Cassandra
Date Fri, 08 Oct 2010 13:06:20 GMT
On Fri, Oct 8, 2010 at 2:12 AM, Peter Schuller
<> wrote:
>> If your C* process dies and/or is killed you should not lose data.  It's
>> written to the commit log before the client is acked, however that entry may
>> not have made it to disk yet in the case of commitlogsync=periodic.  So, if
>> you kill the C* process you're fine.  If you nicely restart the OS, you
>> should be fine (assuming your boxen/raid controllers/disks/etc do the sane
>> thing).  If you nuke your OS, then see above about losing data on CL.ONE.
> Being fine in case of killing Cassandra does depend though on
> Cassandra still guaranteeing that it write():s to the fd prior to ack
> even in periodic mode. I haven't checked, but I sort of took the
> default position of assuming it did not unless otherwise specified.
> If it does, and if this is an intended guarantee, that's great (and
> I'll happily submit a patch to make this explicit in docs/comments).
> Can anyone confirm/deny that this is an intended guarantee?

It is not.

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support

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