From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On 
Behalf Of fred johanson
>The guys next door are rolling out our pilot project Exchange
>server.  Right now they're comfortable with the TDP and its
>capabilities.  For the near future, differential backups with 
>an occasional
>full backup to truncate the Exchange log will suffice.  But they wonder
>what happens when they move from a few dozens users to hundreds or
>thousands, and the "data\0001\Public Folder Store" approaches 
>the Tb range
>or larger.  Will there be enough hours in the day to do a full 
>backup?  If
>not, how does the log get truncated?  They're already asking about
>Flashcopy and NAS and large images.  All answers are appreciated.

A strong word of encouragement:

Do not let your Exchange environment evolve into one store running in
the TB range. Break up your storage groups into several smaller storage
groups, or (better yet) use multiple Exchange servers. This not only
makes sense, but it's also the Microsoft recommendation.

As an example, let's use 3 hours as a maximum for "reasonable" full
backups. Assuming you can get 5MB/sec on backups (actually a little slow
for a 100Mb network):

  3 hours = 10800 seconds x 5MB/sec = 54GB for a 3 hour backup

These are conservative stats. The customer I'm adminning TSM for right
now got one of last night's information store backups (of 82.8GB) in
8440 seconds--almost 10MB/sec--on a 10/100 network.

Further:
I would not bother with differential backups. One full backup per day,
with perhaps an incremental backup 12 hours after the full, would
guarantee a maximum of 12 hours of data loss in the event of a
catastrophe and subsequent restore. (Of course, you could do a daily
full, and incrementals at 8 and 16 hours after the backup, for even
greater minimization of data loss.)

--
Mark Stapleton (stapleton AT berbee DOT com)
Office 262.521.5627