Circular logging must be disabled if you want to do the following:
Run incremental and differential backups.
Recover data up to the point of failure.
Run continuous backups of Information Store transaction logs.
Put transaction log files on a separate physical disk from the database. If the disk that contains the database is damaged, the transaction logs are available as a recovery resource.
Set the retention period for deleted items and mailboxes to a length of time that is appropriate for the available disk space. The longer the retention period, the more disk space is required. However, some retention period can prevent you from having to restore a mailbox or database. If possible, configure the Exchange server so that items are not deleted until a full backup is performed.
Make Write Cache unavailable on the SCSI controller. Data corruption can occur if the computer fails before the operation is written to disk.