Tammy,
I backup Exchange 2k (dual xeon), to a NetBackup DC 4.5mp3 on Solairs 
(e280), writing to LTO1, using gigabit ethernet, and I do one data 
stream for about 200 mailboxes.  The mailbox backup is about 50GB, takes 
6 hours, and when I have watched it run, it usually puts a 40% load on 
the server.  We also plan to recover the database in the event of a 
disaster, in the manner you have described.

What kind of hardware do you have that can tolerate 80 streams?
I have noticed that searching through the mailbox tapes for a specific 
user's set of data can take up to 20 minutes.  The tape drive is moving 
along very quickly while looking for the data set. 
Our mail server requirements allow plenty of time for the mailbox 
backup, so six hours is not unreasonable for us.  I would split it into 
2 or 3 streams next if we had to improve backup times.
I've seen tremendous improvements in restore speeds when pulling several 
data streams from a tape going to the same target.  An oracle database 
that takes 6 to 8 hours to backup with one stream can be accomplished in 
1.5 hours with ten streams (ten mountpoints).  Recovering that image to 
another host of near equal power, takes almost 2 hours.  I set 
multiplexing to 5 so it would write to 2 drives simultaneously, and NB 
was clever enough to load both tapes for reading when I did the restore.

-Jon




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System: Windows 2000 w/NetBackup DataCenter 4.5.3
Library: STK L40 w/4 320 SDLT drives
 
Question:  I am currently backing up 700+ mailboxes on an Exchange 5.5 
server.   I have Microsoft Exchange Mailboxes:\* under pathname or 
directories within the policy.  Media multiplexing is set to 20, so 
roughly 80 mailboxes can be backed up simultaneously.  This has cut my 
Exchange backups times down from 8 hours to 2.5.    In a disaster 
situation I would just recover the whole database and catalog files. 
 
Pros: Faster backup times, Faster restore times of individual mailboxes.
 
Cons: Larger catalog, slower catalog backups, Locating the mailbox to be 
restored takes longer.
 
My question is, are there additional cons/downfall that I am not 
thinking of?  I want to make sure I am not doing more harm to my system 
than needed.
 
Is anyone else doing this?
 
Your comments are appreciated.