Mike,

Without commenting on the merits of your proposal, I share your concern
about collocation causing elevated tape mounts and consequently elevated
wear and tear on tapes.  We have seen this first hand, and it is of
increasing concern to us.  For those of you with relatively smaller tape
volume sizes, you should consider this too, because eventually you may end
up replaceing your current tape technology with newer tape technology.  New
tapes hold increasingly more amounts of data, and this will exacerbate the
problem.  Let me explain why.  As tape capacity goes up, the number of
clients you will end up sharing a tape volume will also go up.  If you are
using collocation, this will result in a higher percentage of your tape
volumes being mounted each time you migrate from disk to tape (assuming, of
course, that you aren't already mounting 100% of your volumes every time!).
 We find that the vast majority of tapes in our tape robot are mounted
every day during migration from disk to tape (we use collocation).  This
increased wear on tapes means that we have to replace tapes more frequently
than we might otherwise have to.  We're still uncertain about this, but it
seems a likely possibility.  Given that new technology tapes aren't cheap,
this can run into a significant expense.  If there were a way to lessen
this problem, it would result in a savings for us in replacement tapes.

..Paul
--
At 09:31 AM 8/21/98 -0500, you wrote:
At 09:31 AM 8/21/98 -0500, you wrote:
>I have seen discussions on this list in the past talking about the need to
>reduce the number of tape mounts on restore. They usually start out by
>asking can ADSM perform full backups? Which in turn usually leads to
>recommendations of collocating tapes. Then it is discussed how collocation
>can lead to greatly increased tape mounts, tape wear & less efficient tape
>utilization and is up to the admin. to weigh the benefits versus the cost.
 (rest omitted)