Exchange runs off of jet_files for both the priv.edb and pub.edb which contain private(mailboxes) and pub(public folders. A backup of exchange is mostly an all or nothing thing.
However, some third parties have come up with creative solutions (e.g., Seagate's Backup Exec for Windows NT and Computer Associates' ARCserveIT) that let you back up one or many mailboxes, either in addition to or instead of backing up the IS and directory databases. These backups, often called brick or mailbox backups, let you restore one mailbox without having to reload the entire IS. That's the good news.
The bad news is that these solutions use Messaging API (MAPI) calls to read each mailbox's messages and then back them up. This process is very slow—the time required to back up an IS as a group of mailboxes can be as much as 50 times longer than that required to back up the same data through NT Backup. In addition, when you start backing up individual mailboxes, the backup data set expands, because you lose the storage savings of the single-instance storage model. The expansion depends on how many messages each mailbox holds and how many messages other mailboxes share. In the worst case (i.e., other mailboxes share every message in the mailbox), the increase can be a factor of four or even more.
So, you can back up individual mailboxes by choosing a third-party Exchange backup solution that supports brick backups. However, the process takes more time and space than backing up the Directory and the IS, and you might find alternative solutions more suitable. If you want to recover an entire mailbox and you don't want to spend the money or time to use a third-party brick backup solution, you can use either .pst or .ost folders or a recovery server.
If you want to be able to restore some mailboxes (e.g., those of your company's executives), you can force their clients to store mail in personal folders (.pst files) on a network server. Then, back up the .pst files as part of your usual server backup rotation. This practice lets you restore the mailbox and any deleted items (if you've enabled deleted-item recovery), but it makes you vulnerable to the loss or corruption of a .pst file. So make sure your backups are usable. You also face the political difficulty of deciding whose mailbox you'll back up.
The method also has some practical obstacles. Personal folders don't allow shared access. Usually, Microsoft's clients close the .pst file after 30 minutes of inactivity, but if other MAPI clients are running, scheduled backups might not be able to back up the file. Another drawback: Users who use .pst files can't share their calendar with server-based users.
Hope this helps........................
