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Re: df hangs -- nfs related problem



On Wed, 2009-01-07 at 10:31 -0800, Aldo Foot wrote:
> On Wed, Jan 7, 2009 at 7:16 AM, Patrick O'Callaghan
> <pocallaghan gmail com> wrote:
> > On Wed, Jan 7, 2009 at 9:33 PM, Rick Stevens <ricks nerd com> wrote:
> >>
> >> Try "lsof | grep nfs" to see if anything has the mountpoint open.  If
> >> not, try "umount -f /mnt/nfs" as the root user to try a forced umount.
> >>
> >> Also check to see if the mount command (or /etc/fstab entry) has "hard"
> >> specified (that's the default as well).  Unless you're really certain
> >> about the stability of the network and of the NFS server, I'd recommend
> >> you specify "soft" in the mount command (see "man 5 nfs" for details).
> >
> > That would depend on which is worse, potentially losing data or having
> > a client machine hang because the server is (perhaps temporarily)
> > unavailable. It depends totally on the specific application scenario.
> > To quote nfs(5):
> >
> > <quote>
> > A  so-called  "soft"  timeout can cause silent data corruption in
> > certain cases. As such, use the soft option only when client
> > responsiveness is more important than data integrity.  Using NFS over
> > TCP or increasing the value of the retrans option  may  mitigate some
> > of the risks of using the soft option.
> > </quote>
> >
> > IOW there is no "right" answer to this.
> >
> > poc
> 
> The command "umount -f" fixed my problem. Thanks Rick.
> I had tried "umount -k", which works in older RedHat8
> boxes; clearly I've got to re-read the man pages now and then.
> 
> So, it appears a soft mount may be ok for read-only operations but not
> ideal for things such as remote X-applicatons or filesystems
> such as /home or /var/mail. It's wise to make the distinction between hard
> and soft mount --great pointer.
----
I have switched over to mostly using automounts which connect/disconnect
when needed and I have been using

-rsize=8192,wsize=8192,intr

as a basic setup. Obviously I could tune the rsize/wsize and perhaps
figure out that a larger number would give me better performance but I
found that the intr option seemed to provide the soft landing when
needed. These are the users home directories and function for a number
of connections/users/systems without any fuss.

Craig


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