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From "Flachbart, Dirk (HP Software - TransactionVision)" <>
Subject Question about insert performance in multiple node cluster
Date Mon, 28 Feb 2011 17:24:19 GMT

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?


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