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Date:      Thu, 1 Aug 1996 11:54:03 +0100 (BST)
From:      Doug Rabson <dfr@render.com>
To:        "Jordan K. Hubbard" <jkh@time.cdrom.com>
Cc:        Tony Jago <tony@fit.qut.edu.au>, freebsd-current@FreeBSD.ORG
Subject:   Re: NFS Diskless Dispare...
Message-ID:  <Pine.BSI.3.95.960801114819.14900E-100000@minnow.render.com>
In-Reply-To: <7102.838894358@time.cdrom.com>

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On Thu, 1 Aug 1996, Jordan K. Hubbard wrote:

> >   1. The inability to mount file systems. The clients start barfing with
> >      something like "RPC mount timeout". This problem goes away after a
> >      while as the clients retry. I think its the mountd getting too many
> >      requests at once. Each client mounts 9 file systems.
> 
> I think that this is a more generic NFS bug in -current.  I can
> reproduce this, even causing mountd to silently exit (no core, no
> syslog msg) with just one client and some fierce AMD-assisted pounding
> on a 2.2-current NFS server.  Debugging this will be challenging, so
> all the help we can get will be useful.  If you can add some extra
> logging to strategic spots in your mountd, perhaps, and analyse the
> data generated you might even find the fix yourself.

Ouch!  This would be pretty hard to reproduce here since I only have one
system which runs -current and most of the time that machine is in Win95
:-(.  Try compiling mountd with DEBUG_FLAGS=-g, then attaching gdb to it
with 'attach pid'.  If it doesn't fault, set a breakpoint in _exit.

> 
> >   2. Files permissions are read incorrectly. Files that should be able to
> >      be executed are giving "permission denied" messages. Sometimes even
> >      the kernel can't be loaded by netboot.com but if you persist by
> >      typing "autoboot" it will magically start to work. Machines fail to
> >      boot correctly as programms called in /etc/rc don't start
> >      (permission denied).
> 
> Probably more NFS bogosity.

I think for diskless root filesystems, you must export the fs with
-root=0, otherwise lots of stuff will break.

> 
> >   3. Pageing in of binaries cause the system to panic. Vnode_pager does
> >      not seem to like it when it can't page in executables, even when the
> 
> See #2. :-)

Probably paging from a file which root can't access (see above).

> 
> >   version 2 with hard mounts. I tryed NFSv3 (both TCP and UDP) for a while
> >   but it was even worse. The servers have 16 nfsd's running and the
> 
> That's not surprising.
> 
> >   clients have 4 nfsiod's. The most stable configuration I have found at
> >   this stage has been 2.2-960612-SNAP but I am open to suggestions.
> 
> 2.1.5?  Its NFS is still unstable, but I don't believe anywhere near
> the state it's in with -current.

I think some of the stability problems with NFS are due to its lack of
vnode locking primitives.  This might be addressed by the lite2 fs work
but if not, I will try to get something in after that work is merged.

--
Doug Rabson, Microsoft RenderMorphics Ltd.	Mail:  dfr@render.com
						Phone: +44 171 251 4411
						FAX:   +44 171 251 0939




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