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From Ryan King <r...@twitter.com>
Subject Re: Question about insert performance in multiple node cluster
Date Mon, 28 Feb 2011 17:30:09 GMT
On Mon, Feb 28, 2011 at 9:24 AM, Flachbart, Dirk (HP Software -
TransactionVision) <dirk.flachbart@hp.com> wrote:
> Hi,
>
>
>
> We are trying to use Cassandra for high-performance insertion of simple
> key/value records. I have set up Cassandra on two of my machines in my local
> network (Windows 2008 server), using pretty much the default configuration.
> I created a test driver in java (using thrift) which inserts a single 1K
> data column (keys are unique strings of integer values) with multiple
> threads. On each machine I am able to achieve around 9,000 inserts/sec when
> running the test driver with the local Cassandra server.
>
>
>
> Then I set up a cluster with both machines, and ran the same test again (the
> test driver is still local to one of the Cassandra nodes). Surprisingly I
> did not see any improvement in the insert performance, I got the same 9000
> inserts/sec as when running with a single node. I know that I shouldn’t
> expect linear scaling to 18,000 operations/sec, but shouldn’t I see at least
> some significant improvement? The CPU isn’t fully loaded on either of the
> machines, and the network utilization is low too (1000 mbit network). Later
> on I also tested adding a third node, but that didn’t improve anything
> either.
>
>
>
> I suspect I’m doing something wrong with setting up the cluster. The only
> changes I made on the second machine were:
>
>
>
> -          AutoBootstrap=true
>
> -          Setting ‘Seed’ to the IP of the other node
>
>
>
>
>
> Did I miss anything? Or am I simply wrong in expecting the throughput to
> scale when using multiple nodes?

What's your replication factor? Which consistency level are you using?
Is the ring evenly balanced? Did you double the number of client
threads when you added the second server?

-ryan

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