Le Mon, 20 Jun 2011 18:08:01 +0200
belcampo <[email protected]> écrivait:

> Do I expect too much ? I thought it should scale more or less lineair.

Yes, first NFS-export goes through the filesystem interface, which
isn't very fast. It's actually quite surprising that you've got such
high performance, because last time I checked NFS over PVFS was quite a
dog... :) -- well to be frank I didn't really test it since version
2.8.

Then you forgot how data flows in such a cluster. When you're pulling
100 Mb/s via NFS, you're necessarily inducing 50 Mb/s of cluster trafic
between the nodes (actually a bit more). So you're basically
dissatisfied getting only with 150% of the maximum network
throughput? ;) What did you expect, ponies? :)

I don't know of any cheapo 100Bt interface actually able to pump 100
Mb/s full duplex (or really 200 Mb/s)...


                       netbook 1                  netbook 2
                         __  _     PVFS 50 Mb/s    __  _ 
                        [__]|=|<------------------[__]|=|
                        /::/|_|                   /::/|_|
                          |
                          |
                          | NFS 100 Mb/s
                          |
                          |
                          v
                      ____   __ 
                     |    | |==|
                     |____| |  |
                     /::::/ |__|



To get better performance in such a setup, you need at least two nics
per node : one for NFS data and one dedicated to cluster communication.

regards,
-- 
------------------------------------------------------------------------
Emmanuel Florac     |   Direction technique
                    |   Intellique
                    |   <[email protected]>
                    |   +33 1 78 94 84 02
------------------------------------------------------------------------

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