[Linux-cluster] Re: [NFS] [RFC] NLM lock failover admin interface

[James Yarbrough <jmy lolita engr sgi com>]

> There seems to be an unstated assumption here that there is one
> virtual IP per exported filesystem.  Is that true?

This is the normal case for such HA services.  There may actually be
a single IP address covering multiple filesystems and/or NFS exports.

> I think that maybe the right thing to do is *not* drop the locks on a
> particular filesystem, but to drop the locks made to a particular
> virtual IP.

For filesystems such as ext2 or xfs, you unmount the filesystem on the
current server and mount it on the new server when doing a failover.
In this case, you have to be able to get rid of all the locks first and
you do that for the entire filesystem.  For a cluster filesystem such as
cxfs, you don't actually unmount the filesystem, so you really need the
per-IP address approach.

> If I want to force-unmount a filesystem, I need to unexport it, and I
> need to kill all the locks.  Currently you can only remove locks from
> all filesystems, which might not be ideal.

This is definitely less than ideal.  This will force notification and
reclaim for all exported filesystems.  This can be a significant problem.

jmy sgi com
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