You could always use Windows Server backup, which is baked into Windows Server 2008 R2.
There's a couple of options as follows:
- I'd really only do this if you're writing to tape. Use Windows Server Backup to backup Exchange, save the data (locally or on a network location) and use bacula to save the backup files to tape.
- If you're saving to network storage, it would probably be easier to just save the Windows Server Backup files on your network storage. This will allow for a direct restore of Exchange and doesn't require bacula as an intermediary, so will be quicker to recover in a disaster scenario.
It is important to use proper tools when backing up Exchange that use the Exchange backup API's, or you'll find your transaction logs won't get flushed and your log volume will rather quickly fill up and dismount the associated databases.
If you are after a commercial solution, personally I use Backup Exec 2010 R2. Others are available, but I haven't really used them enough to comment on functionality. As with all commercial software though, you'll end up paying for the privilege and it's ultimately up to you whether this is something you'd consider.