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From "David Dabbs" <>
Subject RE: Experiences with Cassandra hardware planning
Date Mon, 25 Oct 2010 07:39:44 GMT
Sorry, Eric I'm not following you. You've set the JVM's processor affinity
so it only runs on one of the processors? 



From: [] On Behalf Of Eric
Sent: Monday, October 25, 2010 12:49 AM
Subject: Re: Experiences with Cassandra hardware planning


We have not started our JVM's with numactl.


I am not sure what (if any) benefit there has been to turning on NUMA in the
BIOS.  Turning it on could have in fact reduced performance.  I suspect that
Java is only using memory from one of the processors (since less than half
of the physical memory is assigned to the JVM) and the other processors
memory is being used for file system cache.


Clearly there is probably some room for improvement here.  We have not
invested much time in this as of yet.


If anyone else has knowledge in this area please chime in!



On Sun, Oct 24, 2010 at 10:36 PM, David Dabbs <> wrote:


Thanks for the detailed post! Did you need to start your JVMs with numactl
in order to take advantage of NUMA?
I know the board, OS and JVM must  be configured properly, but it's not
clear if the JVMs must be started with numactl.



From: Eric Rosenberry []
Sent: Sunday, October 24, 2010 10:17 PM
Subject: Experiences with Cassandra hardware planning


Over the past nine months I have been working to tune our hardware
configuration to optimally balance CPU/RAM/disk/iops/network per node for
our Cassandra workload.  Thanks much to those here who have provided helpful

I wanted to share back to the community some of the learnings we have come
across including the hardware configuration we have been successful with
(YMMV).  This is still a work in progress naturally.

I have written up a detailed blog post about this here:

Here are the highlights:
. Dell C1100 "cloud series" servers with 10x 2.5 inch drive bays
. OCZ Technology Vertex 2 MLC SSD's with the Sandforce 1200 series
. Arista Networks 7048 1U Top of Rack switches running MLAG with LACP to the
Let me know if you have any questions!



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