> I think that my words have been taken out of context. I know you cant
> and shouldn't mix retentions on media which is why i find it hard that
> people use 1 media pool for all backups. From that i would assume they
> have the same retention for all backups. This in my opinion which is
> only my opinion is a bad idea.
> 
> To give advise to the original thread i was saying that one 
> volume pool
> for all backups is perhaps not the right way to do things and i was
> surprised by the number of people who seemed to adopt it.  I 
> asked about
> mixed retentions as people with 1 volume pool cannot ( safely ) then
> have a full backup with a different retention than say a 
> cumulative backup.

Dave, perhaps I'm dense, but I read the above the same as I read your
original statement:  it seems you are saying that a 1-month-retention
full can wind up on the same tape as a 1-week-retention cumulative.
There's no "safely" about it--that _does_ _not_ _happen_ unless you
force it with use_multiple_retentions_per_media.  Has nothing at all to
do with volume pools.

Please, what am I misunderstanding about what you are saying?

> > What about them?  NetBackup *never* puts different 
> retentions on a tape
> > unless you force it to with the 
> MULTIPLE_RETENTIONS_PER_MEDIA directive
> > (and there are very few situations where that's a good idea).

And someone asked when that would ever be a good idea.  Two that I've
found are

o  small robots.  Maybe it's worth having some full, out-of-the-robot
tapes with mixed retentions sitting around until the longest/newest
image on it expires versus having, say, eight partial tapes clogging up
slots in the robot (say, MediaA and MediaB, each backing up clients with
1-week and 1-month retentions in two pools.  Throw in
mux/non-multiplexed, a few more pools, a few special retentions, another
media server, and ... well, a 30-tape robot just won't cut it for that
customer.  If you allow multiple retentions, you free up precious slots.

o  moving day.  A couple of clients are moving to another NetBackup
domain, or maybe you're sending backups to a DR site.  If you make, or
dup, their dailies, weeklies and last monthly (w/different retentions),
it's three tapes--or one if you put them all on one tape.

In short, "multiple retentions per media" doesn't hurt a darned thing,
ever.  It just means that a tape of 1-week-retention dailies that has a
1-month-retention weekly on it at the end won't become available for a
month, rather than a week.  And _that_ is intrinsically no different
than the "waste" of older images at the beginning of a single-retention
tape being held hostage to the expiration time of the last image.