On Aug 31, 2007, at 4:33 PM, Dave Mussulman wrote:

... Avamar said their software got
10-20% reduction on a backup of a stock Windows XP installation.  A
single system, say it's the first one you added to your backup group.
That's not two users with the same email attachments saved, or
identical
files across two systems - that's hashing files in the OS (I presume
from headers in DLLs and such.) ...

I'm mildly amused that in all these postings on the subject, none has
addressed the corollary of the backups: restoral.  There are likely
some implications in the restoral of files backed up this way,
perhaps most particularly in system files; and restoral performance
is also something one would wonder about.  And there may be
situations where such a backup/restore regimen is to be avoided,
because of issues.  Perhaps those with experience in this area would
post what they've found.

   Richard Sims, at Boston University