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Old 01-02-2010, 02:55 PM
Chris Davies
 
Default Slow NFS

I'm curious whether anyone has good a decent read/write speed using NFS
(v3 or 4) between a number of Debian "testing" based systems.

I've got one box exporting a number of filesystems using NFS v3, and
three others mounting various combinations of those file systems. I
see less than 10% disk throughput on the remote boxes that on the local
one. Switched gigabit LAN throughout.

I'd expect some hit, but 90% degredation seems awfully high.

Would migrating to NFS v4 help any? If anyone can offer suggestions,
I'll happily offer more details of my setup.

Thanks,
Chris


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Old 01-02-2010, 04:33 PM
Robert David
 
Default Slow NFS

Post your /etc/exports from some machine that has slow traffic.

Is this only for nfs? Try copy some file with scp and compare the speed (it
should be slower than nfs). Because this may not be nfs problem.

I use nfs in a lot of machines, also for sharing users home folders. And
doesn't have any problem (debian lenny servers, gentoo servers, ubuntu pc's,
debian testing ps's). I do not have any squeeze nfs server. But nfs is always
the fastest sharing I have.

I dont think nfs v4 can help here.

Robert.

Dne So 2. ledna 2010 16:55:18 Chris Davies napsal(a):
> I'm curious whether anyone has good a decent read/write speed using NFS
> (v3 or 4) between a number of Debian "testing" based systems.
>
> I've got one box exporting a number of filesystems using NFS v3, and
> three others mounting various combinations of those file systems. I
> see less than 10% disk throughput on the remote boxes that on the local
> one. Switched gigabit LAN throughout.
>
> I'd expect some hit, but 90% degredation seems awfully high.
>
> Would migrating to NFS v4 help any? If anyone can offer suggestions,
> I'll happily offer more details of my setup.
>
> Thanks,
> Chris
>


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Old 01-02-2010, 09:33 PM
Andrew Reid
 
Default Slow NFS

On Saturday 02 January 2010 10:55:18 Chris Davies wrote:
> I'm curious whether anyone has good a decent read/write speed using NFS
> (v3 or 4) between a number of Debian "testing" based systems.
>
> I've got one box exporting a number of filesystems using NFS v3, and
> three others mounting various combinations of those file systems. I
> see less than 10% disk throughput on the remote boxes that on the local
> one. Switched gigabit LAN throughout.
>
> I'd expect some hit, but 90% degredation seems awfully high.

There is a performance-tuning section in the NFS Howto,
with several tips, including simple tests for measuring performance.
<http://nfs.sourceforge.net/nfs-howto/ar01s05.html>

My own experience with NFS on a server with several tens of
clients is that the biggest determiner of performance is the type
of file operations you're doing. Anything that requires many
seek operations, like grepping for complicated regular expressions,
or writing data character-by-character, will do very poorly.
Things that operate sequentially, or in very large chunks, do
much better. In general, copying is fast, searching is slow.

I think NFSv4 is much the same, although it may introduce
a few more options, and so be more tunable. I have no direct
experience with it.

-- A.
--
Andrew Reid / reidac@bellatlantic.net


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Old 01-04-2010, 08:48 PM
Chris Davies
 
Default Slow NFS

Andrew Reid <reidac@bellatlantic.net> wrote:
> There is a performance-tuning section in the NFS Howto,
> with several tips, including simple tests for measuring performance.
> <http://nfs.sourceforge.net/nfs-howto/ar01s05.html>

Thanks for the reminder. Somehow I'd missed that section of the Howto.


> My own experience with NFS on a server with several tens of
> clients is that the biggest determiner of performance is the type
> of file operations you're doing.

A Java compile on a tree mounted via NFS is the biggest hit (IO bound,
not compute bound!). There's the usual edit stuff associated with a
perl/html website, but that's one (small-ish) file at a time and the
delay is not so noticeable. Oh, and a development installation of ORACLE
RAC is using another NFS partition for its stuff, but again this isn't
very heavy usage.

One thing that I discovered from the NFS Howto is that our NFS
server was running only a single nfsd thread. That, despite the
/etc/default/nfs-kernel-server file having a definition of
RPCNFSDCOUNT=8. I don't see why the 8 is being ignored in favour of 1,
but that's for another day.

Thanks,
Chris


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