Just a small point to throw in to the melting pot.

How do you measure tape usage. Simple, look at the number of times a volume has
been mounted in the query volume format=detailed output.

Now, if you are running DRM, look at the counts for a tape that has been
through your vault and returned through reclaimation. Arrrrgh.. No information
remains!

ADSM looses track of all usage counts when a volume is deleted from a storage
pool. This happens whenever a reclaimed volume is put back in the scratch pool
(from any pool, not just copypools), and also if a database copy tape is
returned.

I've just had my first 3570 tape report media errors after 6 months of
use-in-anger. And I don't know how many times it has been used. What I am
worried about is the other 199 tapes that were purchased at the same time.
Should I replace them all now!. I'm not sure my employer will take kindly to
#7000+ to replace them all after just 6 months!

I issued a problem for this, and apparantly it will be a DCR, and added in a
future release, but other people really need to know for the type of problem
that is being discussed here.

Peter Gathercole
Open Systems Consultant.

Paul Zarnowski wrote:

> 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:
> >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)