From: Greinig, Peter (Peter.Greinig@bourne-leisure.co.uk)
Date: Mon Dec 02 2002 - 09:43:34 EST
All,
Thanks to Martin Petder, Peter Gergen, Johan Brusche, Thomas Sjolshagen,
Mark Deiss and Pat O'Brien for their responses.
The general conclusion is that mounting a fileset on more than one
(unclustered) node simultaneously is not a good idea at all! (I didn't think
it was either...) Pat O'Brien went one stage further and actually tried it
out (you're braver than I am!!!), Pat's conclusion being that with two
different systems writing to the same disk one cannot see the changes made
by the other and eventual corruption is the result.
Given that my whole reason for having this storageset available to any of
the three machines is to be able to move data around without it going over
the LAN (so ruling out NFS mounts etc) then I am proposing the following
(suggested by most of the people above):
1. No entry in /etc/fstab for this domain/fileset on ANY machine
2. A daemon process running on each machine which will be responsible for
mounting the fileset on that machine. For this process to mount the fileset
it will have to receive a 'not mounted' response from BOTH other machines.
3. A simple interactive script which will place a mount (or unmount) request
with the above daemon.
4. Communication between the interactive scripts & the three daemons to be
done using RCP or small NFS mounts.
5. Tell anyone with root access (fortunately very few people) that if they
even THINK of mounting the fileset manually then bits of them will be cut
off (!)
Given that all data on this fileset is transitory, i.e. we can afford to
loose it, then I think this will be the best approach. Thomas Sjolshagen (HP
Tru64 engineer) suggested that corruption could cause an AdvFS IO domain
panic, but that this shouldn't cause a general system panic (unless
live_dumps set to 0 in sysconfig) - I'm happy to live with the possibility
of domain panics...
Again, thanks for the responses.
Regards,
Peter Greinig.
Systems Programmer
Bourne Leisure Group Ltd
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