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Date: Wed, 09 May 2007 18:20:38 +0200
From: Fabian Wenk <fabian@wenks.ch>
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To: Seraphi <seraphi.lord@gmail.com>
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Cc: freebsd-amd64@freebsd.org
Subject: Re: amd64/112528: NFS over TCP under load hangs with "impossible
 packet	length"
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Hello Seraphi

Seraphi wrote:
>>Number:         112528
>>Category:       amd64
>>Synopsis:       NFS over TCP under load hangs with "impossible packet length"

Just a side note to NFS with Gbit Ethernet:

The manpage of nfs(5) on Suse Linux has an interesting section 
about "Using NFS over UDP on high-speed links such as Gigabit can 
cause silent data corruption.". See the "WARNINGS" Section at the 
end of the manpage [1] for more.

   [1] 
<http://manpages.unixforum.co.uk/man-pages/linux/suse-linux-10.1/5/nfs-man-page.html>

If the clients are Linux with Kernel 2.4.x then NFS over TCP is 
very slow compared to UDP. With Linux Kernel 2.6.x the performance 
of NFS over TCP is the same as with NFS over UDP. Do not forget to 
set /proc/sys/net/ipv4/ipfrag_time to 2 on Linux clients when 
using NFS over UDP on Gbit Ethernet.


bye
Fabian