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To: Terry Lambert <tlambert2@mindspring.com>
In-Reply-To: Your message of "Tue, 25 Mar 2003 18:52:59 PST."
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Date: Wed, 26 Mar 2003 10:21:21 +0000
From: Ian Dowse <iedowse@maths.tcd.ie>
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cc: current@freebsd.org
Subject: Re: NFS -current 
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In message <3E81160B.E5406C60@mindspring.com>, Terry Lambert writes:
>Ian Dowse wrote:
>> It is normal enough to get the above 'not responding' errors
>> occasionally on a busy fileserver, but only if they are almost
>> immediately followed by 'is alive again' messages.
>
>This is arguably a bug in the FreeBSD UDP packet reassembly code
...

Actually, I was referring here to an effect that occurs when the
time taken by the server to complete requests varies in a particular
way. The NFS client may observe a large number of requests all
answered within a few milliseconds, so it starts using short timeouts.

Then for some reason (usually a long list of outstanding disk-intensive
operations), the server takes a few seconds to complete the next
request. Within this time, the client repeatedly times out, retransmits
the request, backs off and repeats, and in extreme cases it is
possible for the client to reach the limit that triggers the "not
responding" warning.

Ian