If you backup Exchange to disk using the Granular Restore Technology option (Enable the restore of individual mail messages and folders), you will find your backup-to-disk folder filling up with .IMG files. Regardless of the media set rules you set for your backup, the files are not overwritten, and continue to accumulate until they fill the disk.
Unfortunately the files created by Exchange's GRT technology simply ignore any media set rules that are in place. The continual creation of new files is by design. Only when the disk becomes full (or the disk space reserve limit is reached) will old files be overwritten. The only workarounds to prevent your disk filling are:
- Manually delete old files (having deleted them from Backup Exec first)
- Allocate a separate disk partition (which you don't mind filling to capacity) for Exchange backup-to-disk backups.
- Set a disk space reserve limit for your backup-to-disk folder