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Date: Thu, 2 Feb 2012 23:44:40 -0800
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Subject: Re: Can you query Cassandra while it's doing major compaction
From: Peter Schuller <peter.schuller@infidyne.com>
To: user@cassandra.apache.org
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> If every node in the cluster is running major compaction, would it be abl=
e to
> answer any read request? =C2=A0And is it wise to write anything to a clus=
ter
> while it's doing major compaction?

Compaction is something that is supposed to be continuously running in
the background. As noted, it will have a performance impact in that it
(1) generates I/O, (2) leads to cache eviction, and (if you're CPU
bound rather than disk bound) (3) adds CPU load.

But there is no intention that clients should have to care about
compaction; it's to be viewed as a background operation continuously
happening. A good rule of thumb is that an individual node should be
able to handle your traffic when doing compaction; you don't want to
be in the position where you're just barely dealing with the traffic,
and a node doing compaction not being able to handle it.

--=20
/ Peter Schuller (@scode, http://worldmodscode.wordpress.com)