On 06/20/11 18:30, Emmanuel Florac wrote:
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,
netbook 1 netbook 2
__ _ PVFS 50 Mb/s __ _
[__]|=|<--------------[__]|=|
/::/|_| /::/|_|
| /
| /
| NFS 100 Mb/s /
| /
| /
v <-----------
____ __
| | |==|
|____| | |
/::::/ |__|
My understanding was, stupid assuming me, that netbook2 could deliver to
the client directly, not via netbook 1.
If I understand correctly, what you're basically saying is that max
throughput with above configuration is always limited to 100Mb/s no
matter how many netbooks I'm using as pvfs2 servers ?
I did compare it to an ancient pvfs2/nfs setup which runs with a
pvfs2/nfs-modified 2.6.17 kernel which resulted in the scaling I was
expecting. I could pull 2.2 -2.4Gb/s from 3 single 1Gb nodes, with copy
or rsync, don't remember exactly. I'll check it tomorrow.
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