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From "Hiller, Dean" <Dean.Hil...@nrel.gov>
Subject Re: compaction throughput rate not even close to 16MB
Date Wed, 24 Apr 2013 20:37:45 GMT
Thanks much!!!  Better to hear at least one other person sees the same thing ;).  Sometimes
these posts just go silent.

Dean

From: Edward Capriolo <edlinuxguru@gmail.com<mailto:edlinuxguru@gmail.com>>
Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Date: Wednesday, April 24, 2013 2:33 PM
To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Subject: Re: compaction throughput rate not even close to 16MB

I have noticed the same. I think in the "real" world your compaction throughput is limited
by other things. If I had to speculate I would say that compaction can remove expired tombstones,
however doing this requires bloom filter checks, etc.

I think that setting is more important with multi threaded compaction and/or more compaction
slots. In those cases it may actually throttle something.


On Wed, Apr 24, 2013 at 3:54 PM, Hiller, Dean <Dean.Hiller@nrel.gov<mailto:Dean.Hiller@nrel.gov>>
wrote:
I was wondering about the compactionthroughput.  I never see ours get even close to 16MB and
I thought this is supposed to throttle compaction, right?  Ours is constantly less than 3MB/sec
from looking at our logs or do I have this totally wrong?  How can I see the real throughput
so that I can understand how to throttle it when I need to?

94,940,780 bytes to 95,346,024 (~100% of original) in 38,438ms = 2.365603MB/s.  2,350,114
total rows, 2,350,022 unique.  Row merge counts were {1:2349930, 2:92, }

Thanks,
Dean





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