> Howdy! I have a question about dynamic volume duplication across cells.
> I'm laying out AFS for the Boulder office of Qualcomm (our main office
> is in San Diego); for a number of reasons our site has its own cell.
> However, there are portions of the San Diego cell that I need to duplicate
> in Boulder; these duplicates should have the same volume names, quotas, and
> mount points as the master in San Diego. Also, the files in this hierarchy
> (which may contain multiple volumes mounted at different levels) need to
> be synchronized to the San Diego masters regularly -- for the sake of the
> argument say once a night. Also, San Diego is updating and adding files
> and volumes to this hierarchy over time.
>
> My question is this: how can I create an automated mechanism to keep
> our tree in sync with San Diego? The mechanism needs to be fairly
> lightweight since it will be run frequently, but it needs to be able to
> detect the presence of newly created volumes in the San Diego hierarchy.
Here's what I think I would do. Note, though, that there are some
restrictions.
- Fetch a new VLDB from the San Diego cell. Notice any volumes which
have been created; someone will have to make a desision as to which
of these, if any, should be mirrored. Also notice any currently
mirrored volumes which have been deleted; again, someone will have to
decide what to do.
- For each volume that is mirrored, examine that volume to see when
it was last changed. If it hasn't been changed since the last time
it was mirrored, there's nothing more to do.
- For those volumes that _have_ been updated, use 'vos dump' in the
remote cell and 'vos restore' in the local cell to do an incremental
update.
As I mentioned, there are some restrictions.
- You must insure that your PTS database contains the same entries as
the one in the master cell. Probably, you want to partition the
user and group ID space between the two cells, so that no one creates
duplicate entries. This could be done by setting the max user and
group ID's in the 'slave' cell, and arranging for some automatic
process to notice updates made in the 'master' cell.
- Any volume which is maintained in the master cell must not be modified
in the slave cell. That probably means that certain heirarchy volumes
(for example, whereever user volumes are mounted) cannot be mirrored.
- Mirroring is on a per-volume level; you can't mirror only part of a
volume using this technique.
- The mirror process will have to be privileged in the master cell.
-- Jeffrey T. Hutzelman (N3NHS) <[EMAIL PROTECTED]>
Systems Programmer, CMU SCS Research Facility
Please send requests and problem reports to [EMAIL PROTECTED]
