[OpenAFS] Re: Volume rename with active volumes
Tue, 6 Sep 2011 09:56:39 -0400 (EDT)
On Fri, 2 Sep 2011, Andrew Deason wrote:
> Clients cache vldb information (which includes name <-> id mappings, as
> well as location information) for 2 hours. So if you're reading or
> writing to a volume when you do the rename, the client will not notice,
> since it knows it is writing to volid 1234, and doesn't care what the
> name is. If you have not accessed the volume recently (or you've issued
> 'fs checkv', or some error causes a re-lookup), it'll try to look up the
> old name and fail.
> Userspace tools look up volume names / ids / etc every time they are
> run, though, so 'fs lq' will interpret the volume id according to the
> most recent information.
> So it's not really "safe" since a client's cache could become stale
> without you knowing, and it would cause accesses to that volume to
> suddenly fail. That failure is a bit unlikely if you do the switch
> relatively quickly, but it is certainly possible. A more safe way to do
> this would be to allow you to add a volume name alias in the vldb or
> something, so you could add the new name, update mountpoints, and remove
> the old name. We don't provide a way to do that.
Richard Brittain, Research Computing Group,
Computing Services, 37 Dewey Field Road, HB6219
Dartmouth College, Hanover NH 03755