From: "Lever, Charles" <Charles.Lever@netapp.com>
Subject: RE: NFS Client Performance Question
Date: Wed, 13 Jul 2005 11:44:14 -0700
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hi chris-

take a look at the NFS faq (http://nfs.sourceforge.net) i believe this
issue is addressed there.

the problem is your itanium uses pages larger than your r/wsize setting,
which forces the client into synchronous I/O mode for NFS.  some
possible workarounds:

1.  upgrade to a late model 2.6 kernel where this is fixed

2.  reduce the page size on your client system

3.  increase the r/wsize to something larger than your page size

4.  compile your client with a larger maximum transfer size so you can
do 3.

the goal is to have r/wsize be equal to or greater than your client's
page size.

> -----Original Message-----
> From: Chris Penney [mailto:cpenney@gmail.com]=20
> Sent: Wednesday, July 13, 2005 2:30 PM
> To: nfs@lists.sourceforge.net
> Subject: [NFS] NFS Client Performance Question
>=20
>=20
> I have a large smp SGI Itanium box box running a 2.4.21 kernel and I'm
> getting fairly bad NFS performance, esp. when doing random writes to
> an unloaded NFS server.  The box is rather busy doing computation and
> a lot of i/o to /tmp; however, there is little network i/o (<100
> KB/s).  I use iozone with the following options to test "-c -e -i 2 -w
> -s 16m" and use an unloaded Sun NFS server (same performance results
> with Linux NFS servers, but they are all under load so I test with the
> Sun).  I only get ~2.5MB/s using the above test.  I found an Intel box
> still running a 2.4.20 kernel and it gets 15MB/s.  On a 2.6 kernel box
> the rate jumps to 46MB/s (nice work).
>=20
> I did some sniffing on the Sun and noticed that the problem Itanium
> system was not doing async writes (snips are from the start of the
> write test):
>=20
> [snip]
> redhat -> server NFS C WRITE3 FH=3D40E5 at 1478656 for 4096 (ASYNC)
> server -> redhat NFS R WRITE3 OK 4096 (ASYNC)
> redhat -> server NFS C WRITE3 FH=3D40E5 at 1179648 for 4096 (ASYNC)
> [snip]
> itanium -> server NFS C WRITE3 FH=3D40E5 at 4239360 for 4096 (FSYNC)
> server -> server NFS R WRITE3 OK 4096 (FSYNC)
> server -> server NFS C WRITE3 FH=3D40E5 at 15101952 for 4096 (FSYNC)
> [snip]
>=20
> The client mount options are:
>    rw,nosuid,bg,hard,intr,nfsvers=3D3,tcp,rsize=3D32768,wsize=3D32768
>=20
> So my question: Is the Itanium system not doing async nfs i/o because
> nfract_sync has been exceeded due to local i/o to /tmp or is it
> something else?  Is there anything I can do to improve NFS performance
> on this box?
>=20
>    Chris
>=20
>=20
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