Umount nfs strangely slow

[Jonathan Ryshpan]

On Fri, 2009-04-03 at 23:11 -0430, Patrick O'Callaghan wrote:
> On Fri, 2009-04-03 at 19:08 -0700, Jonathan Ryshpan wrote:
> > I am mounting a few filesystems from one F10 machine to another.  Mount
> > works rapidly but umount of each of the filesystems takes about 20
> > seconds.  Is this normal?  Could I have the systems misconfigured in any
> > obvious way?  Both machines have x86_64 processors.
> > 
> > Here is the file /etc/exports on the server machine:
> >         /                              amito(ro,sync,no_root_squash)
> > and here is the corresponding mount command on the client machine:
> >         # mount -t nfs claremont:/        /mnt/claremont
> > Here is a typical umount command on the client machine:
> >         # time umount /mnt/claremont/
> >         real	0m21.029s
> >         user	0m0.001s
> >         sys	0m0.004s
> > 
> > Any ideas?  Thanks - jon
> 
> Flushing write data because of sync? Is it equally slow if you just
> mount and immediately unmount with no intervening activity?

There was not activity between the mount and unmount; no other commands
intervened.

jon