>Our requirements are to archive data for about 30 years. TSM is in
>discussion because we use it already for backup...

That kind of situation is very problematic, in all respects.
You will basically have to commit to freezing the hardware and
software technology upon which the backup is based, and the
environment in which it runs, in order to expect to retrieve the
data that far in the future.  Consider, for example, how many of
us still have 7-track, open-reel tape drives and the operating
system and driver cards ready to retrieve data from such tapes.
I have never seen a software vendor commit to maintaining software
such that it will be able to viably handle data written decades
earlier.  Keep in mind also that products such as TSM write the
data in proprietary, unpublished form, which prevents retrieval
by other means.
    Richard Sims, BU