We don't have NetApp equipment, but from what I learned in their
presentation, they have impressively high-performance data servers.
Written by some of the people who developed AFS, the boxes employ
file system techniques which massively cache data, find it fast, and
provide fast access.  It should be connected to your system via
comparably fast networking, such as 100mb ethernet, or ATM.
As a superset of AFS, they provide Snapshot capability, which allows
you to secure a read-only image of each file system at will, and thus
have a stable image for backups.
    I searched their web site, but they have no information on usage
with ADSM or AIX, which is two demerits for them.  (As a customer you
should contact them to address these subject areas in their information
sources.)  In any case, the NFS access should be rapid, but of course
your ADSM client will have to content with increased amounts of data
and numbers of files.  You may want to consider using virtualmountpoints
to logically subdivide larger file systems to parallelize your backups
and restorals.  In general, approach it like any large client data
store.
        Richard Sims, BU