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Date:      Mon, 12 Oct 1998 21:05:08 -0700 (PDT)
From:      dan@math.berkeley.edu (Dan Strick)
To:        current@FreeBSD.ORG
Cc:        dan@math.berkeley.edu
Subject:   -current NFS problem
Message-ID:  <199810130405.VAA18347@math.berkeley.edu>

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I haven't reported this before because it is kind of hard to be
very specific about the cause and because I am under the impression
that people are aware of NFS problems in a general way.  I am reporting
this now necause I believe this to be very important and I haven't
heard any discussion of this specific problem.

There is some sort of NFS problem that causes processes to wedge
in a high priority (i.e. non-interruptable) wait state.  I encounter
this problem whenever I use the ncftp2 program on a 3.0-SNAP or BETA
system to make copy of a FreeBSD release in a remotely mounted file
system.  It doesn't happen immediately, but it always happens before
the copy is complete.  The ncftp2 program just stops reporting any
progress and a ps shows it to be in a "disk" wait state.  The ncftp2
program is normally not killable and attempts (on the 3.0-SNAP or BETA
system) to examine the directory it was copying into also wedge in a
"disk" wait state.  Eventually the entire 3.0-SNAP or BETA system
will wedge.  I suspect the NFS problem, which initially is localized
to one file or directory, cascades through the automounter.

The NFS server, a sun workstation running Solaris 2.5, does not
appear to be affected.  The directory that is wedged on the
3.0-SNAP or BETA FreeBSD system is visible and behaves normally
on the server even after the FreeBSD NFS client system locks up.

The only (temporary) fix is to reboot the FreeBSD 3.0-SNAP or BETA
system and restart the ncftp2 program where it left off.  Eventually
it will finish.  I normally avoid the problem entirely by doing
my FreeBSD release copies on a 2.2.7-RELEASE system which never
hangs.

Note: after a NFS wedge, I never find a partially written file.
The wedge always seems to happen "between" files.

Dan Strick

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