Optional parameters that can be specified at the end of the command line will allow SBS to backup the Exchange Information Store and Directory Store without shutting down the Exchange Server. This has the advantage of clearing the transaction log files once the backup is completed and is the Microsoft preferred / supported method for backup of Exchange. It does not shutdown the Exchange Server and therefore does not require down time to perform the backup.
ntbackup backup c: ds \\server is \\server /b /d”Nightly Backup of SERVER ” /hc:on /e /t Normal /l “c:\SERVER.log”
The DS\\server tells NTBACKUP to backup the Exchange Directory Service from the server called server whilst the IS\\server tells NTBACKUP to backup the Exchange Information Store (both private and public). The other options are listed in the help file for NTBACKUP