Thank you Robert and all others who replied to my question.

What will happen if I add nodetool cleanup to run periodically (similar to nodetool repair) ? Will node tool cleanup consume lot of IO and CPU even though there is nothing to clean ?

Thank you
Emalayan 


From: Robert Coli <rcoli@eventbrite.com>
To: user@cassandra.apache.org; Emalayan Vairavanathan <svemalayan@yahoo.com>
Sent: Monday, 10 June 2013 5:15 PM
Subject: Re: [Cassandra] Expanding a Cassandra cluster

On Mon, Jun 10, 2013 at 3:13 PM, Emalayan Vairavanathan
<svemalayan@yahoo.com> wrote:
> I suspect that nodetool cleanup is IO intensive. So running nodetool cleanup
> concurrently on the entire cluster may have a significantly impact the IO
> performance of applications.

cleanup is a specific kind of compaction, and as such respects the
compaction throughput throttle.

The compaction throughput throttle is designed to prevent compaction
from negatively impacting the performance of things-not-compaction. If
you notice that cleanup compaction on all or most nodes consumes too
much i/o, reduce the throttle value.

=Rob