[lug] NFS cross-mounts

[Vince Dean]

I'm working with a small cluster of Linux servers and desktop machines.
Most of the machines export some of their local file systems to all the
others via NFS.  The intent is that the disks on each machine are
resources which should be shared with all the users.

This results in what is known as NFS cross-mounts, where two machines
each depend on an NFS mount from the other.  Our administrators are
concerned that there is a considerable risk of deadlocks which can only
be resolved by rebooting one or more machines.  However, my copy of the
O'Reilly book "Managing NFS and NIS" claims that "This deadlock problem
goes away when your NFS clients use the automounter in place of
hard-mounts.", page 415.

Are NFS cross-mounts evil even if you use the automounter?

There is a larger issue here: whether it makes sense to have such cyclic
dependencies, especially involving desktop machines, at all.  That
arrangement puts us in a situation where shutting down one machine will
inconvenience an unknown number of users on other machines. You could
make a strong case that machines should only depend on services which
are provided by carefully-maintained servers in machine rooms, and that
the dependencies should should be simple and should form an acyclic graph.

We're working on that larger design question and I'd appreciate any
comments.

Thanks,
Vince