To successfully back up or restore an operation, you must follow some best practices:
Ensure that the raw storage capacity of your tape exceeds the compressed storage capacity of your database by a comfortable safety margin. If it does not, plan for tape changes when doing backups.
Routinely clean the tape drives according to manufacturer specifications.
Do not overuse tapes. Discard them after they reach the maximum number of cycles specified by the manufacturer.
Store the tapes in a safe and accessible location.
Check your backup logs every day to ensure the Exchange backups were successful from the previous night.
Perform a trial backup and restore on a monthly basis to ensure your hardware is working and to keep your restore skills up to snuff.
Document your backup and restore procedures.