My 2 cents on ADSM and a virtual tape solution:

As far as I know, the main goal of a VTS is to merge all
the datasets which are around on many tape volumes into
as few real tape volumes as possible.
While this makes a lot of sense, as long as the (then
virtual) tapes are not filled up with data - it almost
makes no sense when the (virtual) tape volumes are filled
up. It then may happen that the actual data is spread over
more than one real tape volumes and this will then decrease
the restore speed. Also we'd keep in mind that ADSM will
reclaim tape space by merging some tape volumes into one -
which will lead to unnecessary overhead within the VTS
(but that was already mentioned).

Any tape usage which tends to use up the volumes and/or
does space reclamation with the tape volumes is served
better with real tape volumes. This includes all Backup/
Archive/Storage Management software.

On top of that - the IBM VTS is as far as I know designed
with ADSM (or a specialized version of it) as the software
in this box is doing a kind of hierarchical storage
management with these virtual tape volumes. So it's not
cascading the data as ADSM V3 servers can - it's in the
end holding ADSM data *-IN-* ADSM - an approach similar to
hold database datasets within another database.
And the copeting VTS systems will be the like, even though
these will not necessarily use ADSM ...

Best regards

Andreas Peikert, Systems Programmer
   aMaDEUS Data Processing GmbH
   P.O. Box,   D-85424 Erding,   Germany
   Fon: +49 (0)8122 43-5805
   Fax: +49 (0)8122 43-3260
   email: apeikert AT amadeus DOT net

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