One alternative to co-location. . .

We are using several non co-located storage pools and one co-located
pool. We limit the number of nodes in each non co-located pool to
reach a good balance between The number of tape mounts required for
migration, and the number of mounts required for the restore of a
single node.
Only our largest and busiest nodes are co-located.

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)