Are your backups going direct to tape? or are they going to disk first.

If they are going to disk first, then when you migrate the data from the
disk storage pool to tape, ADSM will sort it out by node, and you only have
a very few tape mounts.

If you are going direct to tape, with multiple clients sending data in
parallel, then I suspect that ADSM is still trying to sort out the data by
client - and dooing all of your tape mounts.

Disk storage pools are very useful for speed.

Cheers, 
        Chris