How to make a backup unbootable

[pwhinson]

I have a firewire drive which I've partitioned into two volumes. I schedule backups from my computer to one volume, and then my itunes library from an attached external drive to the other volume. Since the external drive has no os on it there's no way superduper could make that backup volume bootable obviously. But it tries to everything and ends the backup with an error message. Is there anyway I can choose an option (I can't find one that exists) that would allow the backup to complete without throwing errors messages at the end when it tries to make the backup volume bootable?

[dnanian]

Did you select some "On successful completion" option for this volume, perhaps? The "bootable" check will not give an error if the drive has no OS on it, but if you try to set it as a startup drive, or restart from it, you will get an error...