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Date: Tue, 18 Dec 2012 15:52:48 +0000
From: Keith Edmunds <kae@midnighthax.com>
To: linux-nfs@vger.kernel.org
Subject: NFS access slow
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Accessing disks locally on a server gives read speeds around 100MB/s,
write speeds around 267MB/s.

Mounting the same disks on the same server via NFS (ie, not using the
network at all) gives read speeds around 30MB/s, write speeds around
80MB/s.

That's about 30% of the local access speed.

Is that to be expected? I'd expect a 10-15% slowdown, but not this much.

This is using NFSv4; using NFSv3 improves the speeds slightly (36MB/s
read, 95MB/s write).

Other parameters we've changed, none of which have a significant impact:

 - UDP/TCP
 - rsize and wsize
 - noatime
 - noacl
 - nocto

If that's an unexpected slow down, where should we be looking?

Thanks.