About deduplication, Mark Stapleton said:
 
> It's highly overrated with TSM, since TSM doesn't do absolute (full)
> backups unless such are forced. If you want maximum bang for your buck
> with dedupe, you need to run an app like IBM CommonStore for Email
that
> will enable SIS (single-instance store) on your email server's data.

I would agree that it is overrated for TSM, but I interpret that to mean
that many people exaggerate its value, not that it has no value.
Depending on your mix of databases and other application backup data,
you can actually get quite a bit of commonality in a TSM datastore.
There's even duplicate data with file backups.  Remember that if you're
storing 10 versions of a given file, a lot of the blocks that comprise
those versions are the same, and those redundant blocks can be
eliminated.

Although there are exceptions on both ends of the spectrum, the general
rule of thumb I've seen is that TSM customers tend to get about 1/2 of
the dedupe ratios that other customers get -- as long as they are
storing all versions on disk.  If they're just using the dedupe disk as
a staging-like device, they'll get crap for dedupe.

Also, if dedupe had no value for TSM, then IBM wouldn't be working on it
for the next version.

---
W. Curtis Preston
Backup Blog @ www.backupcentral.com
VP Data Protection, GlassHouse Technologies