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Subject: Re: Cassandra benchmarking on Rackspace Cloud
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From: David Schoonover <david.schoonover@gmail.com>
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Date: Mon, 19 Jul 2010 17:45:32 -0400
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To: user@cassandra.apache.org

> Now keep adding clients until it stops making the numbers go up...

Neither adding additional readers nor additional cluster nodes showed =
performance gains. The numbers, they do not move.


--
David Schoonover

On Jul 19, 2010, at 5:18 PM, Jonathan Ellis wrote:

> Now keep adding clients until it stops making the numbers go up...
>=20
> On Mon, Jul 19, 2010 at 2:51 PM, David Schoonover
> <david.schoonover@gmail.com> wrote:
>> Sorry, mixed signals in my response. I was partially replying to =
suggestions that we were limited by the box's NIC or DC's bandwidth =
(which is gigabit, no dice there). I also ran the tests with -t50 on =
multiple tester machines in the cloud with no change in performance; =
I've now rerun those tests on dedicated hardware.
>>=20
>>=20
>>        reads/sec @
>> nodes   one client      two clients
>> 1       53k             73k
>> 2       37k             50k
>> 4       37k             50k
>>=20
>>=20
>> Notes:
>> - All notes from the previous dataset apply here.
>> - All clients were reading with 50 processes.
>> - Test clients were not co-located with the databases or each other.
>> - All machines are in the same DC.
>> - Servers showed about 20MB/sec in network i/o for the multi-node =
clusters, which is well under the max for gigabit.
>> - Latency was about 2.5ms/req.
>>=20
>>=20
>> At this point, we'd really appreciate it if anyone else could attempt =
to replicate our results. Ultimately, our goal is to see an increase in =
throughput given an increase in cluster size.
>>=20
>> --
>> David Schoonover
>>=20
>> On Jul 19, 2010, at 2:25 PM, Stu Hood wrote:
>>=20
>>> If you put 25 processes on each of the 2 machines, all you are =
testing is how fast 50 processes can hit Cassandra... the point of using =
more machines is that you can use more processes.
>>>=20
>>> Presumably, for a single machine, there is some limit (K) to the =
number of processes that will give you additional gains: above that =
point, you should use more machines, each running K processes.
>>>=20
>>=20
>>=20
>=20
>=20
>=20
> --=20
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com