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Re: Stress test in ltsp

On Wed, Apr 16, 2008 at 07:35:28PM +0200, José L. Redrejo Rodríguez wrote:
> In the last two weeks I've been doing some stress tests in the
> classrooms where I'm using ltsp, and I'd like to share the results and
> my conclusions. 
> When using a 1 Gbps port in the switch to connect the server to the thin
> clients:
> - THere was some 98 Mbps NFS peaks, and some 124 ssh peaks, but they
> didn't last in time. All the clients started, no one was stalled. The
> starting time was reduced from 1'40" to 45" with the Open Office
> application running.
> - There was a ¿funny? result: the Xeon machine raised its CPU use to
> 100% when Openoffice started, with the Quad Core  the CPU didn't raise
> more than 20%. Because of it, when using the Xeon server some of the
> clients where stalled for several seconds when starting X. Anyway, the
> starting time was about 5" less when using the Xeon for the clients that
> didn't stall.
> Conclusions:
> - The Xeon server seems to behave better in network use, but worse when
> starting big desktop applications with a lot of graphics.
> - RAM is not very important. The use of RAM was never more than 2
> Gbytes, remaining more than 1,8 Gbytes of not used RAM.
> - When there's no concurrency, both the Xeon and the Quad Core have not
> CPU problems, less than 5% starting OpenOffice (even if some other
> instances are already started), but when there is concurrency, the Xeon
> server behaves much worse. I don't know the reasons and would like to
> know any opinion. 

i'm wondering if there are differences in the on-board sata that is
causing a disk i/o issue... could try "dstat", which can report on
various types of i/o...

could also copy the server's /opt/ltsp to a tmpfs and turn off the
server's swap, and see if that makes a difference in performance, as the
client OS will be loading from the server's ram.

i'd also be curious to see the performance using an i386 machine rather
than amd64, or the same servers with an i386 install of debian.

good luck!

live well,

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