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From malcolm smith <malsm...@treehousesystems.com>
Subject Re: Cassandra benchmarking on Rackspace Cloud
Date Mon, 19 Jul 2010 18:52:22 GMT
Usually a fixed bottleneck results from a limited resource -- you've
eliminated disk from the test and you don't mention that CPU is a serious
issue, or memory for that matter.

So for me that leaves network i/o and switch capacity.  Is it possible that
your test is saturating your local network card or switch infrastructure.

Some rough numbers would be that 1Gbe does about 120MBytes/second i/o in
practice and 100Mbit will do something like 10MB/sec so if your requests so
37,000 requests per second would mean 270 bytes per request (including
network encoding and meta data) on a 100Mbit network or 3.2K per request if
you have a full 1Gbe network including switch capacity to switch 1Gbe per
node.

Is is possible that you are moving 3.2K per request?

-malcolm

On Mon, Jul 19, 2010 at 2:27 PM, Ryan King <ryan@twitter.com> wrote:

> On Mon, Jul 19, 2010 at 11:02 AM, David Schoonover
> <david.schoonover@gmail.com> wrote:
> >> Multiple client processes, or multiple client machines?
> >
> >
> > I ran it with both one and two client machines making requests, and
> ensured the sum of the request threads across the clients was 50. That was
> on the cloud. I am re-running the multi-host test against the 4-node cluster
> on dedicated hardware now to ensure that result was not an artifact of the
> cloud.
>
> Why would you only use 50 threads total across two hosts?
>
> -ryan
>

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