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From Peter Schuller <>
Subject Re: Newbie Question about restarting Cassandra
Date Fri, 08 Oct 2010 07:12:14 GMT
> 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?

/ Peter Schuller

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