Hi John,
If you backup to the Backup-to disk folder then the data gets backed up in .bkf format on the hard disk in a folder.
If you backup to tape then data is backed up in .mtf format.
So if you are planning to backup the data backed up to the hard disk to a tape then only the .bkf files will get backed up to tape and not the actual data. You would face problems while restoring this backed up data as you first have to restore the .bkf files and then restore the actual data again. This would be pretty time consuming.
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