Eric - No, there isn't an easy way (the SIS counter is not particularly accurate). You could do it by:
1. Grabbing the logical size of the mailboxes via ESM or EMS.
2. Grabbing the database size via eseutil /ms (see
http://support.microsoft.com/kb/192185 for more info, but remember to deal with your page size version E2K3-4KB,E2K7-8KB,E2010-32KB).
3. Compare these two values with the physical database size, excluding the free space.
Chad-Thanks for the catch. I've corrected it.
v-9twagh - I would take a look at
http://technet.microsoft.com/en-us/library/bb125040.aspx with respect to Online Maintenance. Also remember that in E2010 you only have VSS solution for backup (quick backup mechanism); as far as restore in the event of an outage, obviously the best solution is mailbox resiliency, but if you aren't deploying that, then you should consider a VSS solution that can restore quickly.
Ross
Microsoft
