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From Mark Jones <MJo...@imagehawk.com>
Subject RE: performance tuning - where does the slowness come from?
Date Wed, 05 May 2010 23:59:58 GMT
My data is single row/key to a 500 byte column and I'm reading ALL random keys (worst case
read scenario)  Cache has minimal effectiveness, so the Bloom trees and indexes are getting
a real work out.  I'm on 8GB Ubuntu 9.10 boxes (64bit).  Yea, I was griping about the performance
earlier, disk is heavily used by Cassandra, so outside of going to some highend SAS stuff,
not sure what to do.

From: Brandon Williams [mailto:driftx@gmail.com]
Sent: Wednesday, May 05, 2010 6:47 PM
To: user@cassandra.apache.org
Subject: Re: performance tuning - where does the slowness come from?

On Wed, May 5, 2010 at 6:36 PM, Mark Jones <MJones@imagehawk.com<mailto:MJones@imagehawk.com>>
wrote:
Have you actually managed to get 10K reads/second, or are you just estimating that you can?
 I've run into similar issues, but I never got reads to scale when searching for unique keys
even using 40 threads, I did discover that using 80+ threads, I can actually reduce performance.
 I've never gotten more than 200-300 reads/second (steady state) off a 4 cluster node.  I
can get roughly 8K writes/second to the same cluster (although I haven't tested both simultaneously
with results worth talking about).

200-300/s is pretty low, especially if you can get 8k writes/s.  I would estimate that you
should be getting at least a couple thousand reads/s.  Here is what I've gotten from a quad
core machine with two disks:

http://racklabs.com/~bwilliam/cassandra/04vs05vs06.png

How much data are you testing with?

-Brandon

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