Jerry Lawson writes

>We have been using collocation for our desktop machine backups, but the
>rapidly expanding number of customers has pointed out to us how wasteful this
>is in our silos.  Therefore, we have decided to turn it off.  In reading the
>Admin GUIDE, the implication was that when I turned off collocation, all of
>the existing volumes in the storage pool that were in "filling" status would
>now be used to satisfy storage needs during the next migration.  Is this
>correct?  In other words - when I run the next migration - ADSM will start to
>mount already allocated tapes that have not been filled up, and continue to do
>this until all of the preallocated tapes are filled, and then it will as for
>a new scratch mount.

>Am I reading this correctly?

Once you turn off collocation, tape selection will be based on the
algorithm for non-collocated storage pools.  The server will try to
select the most full volume that is in filling state.  However, if
a file must span to a second volume, the server will attempt to use
an empty tape for the spanned-to volume; this is done to minimize
the chance that a third tape will be required for this file.
The volumes that are currently in filling state will eventually be
filled, and you should be left with a small number of filling
filling volumes.

>I am a little concerned about this, because it would seem that for a while,
>migrations will ask for lots of tape mounts until the pool is full.

I don't understand the concern.  Migration will probably require fewer
volume mounts, since it will not be necessary to mount a new tape
for every node.  In general, each migration process will require only
a single output tape at any given time.

Dave Cannon
ADSM Development