Comment by xenadu02

This seemed to be a point of confusion in the original story and the video wasn't super clear but:

Pretty much all tape backup software writes headers as it is streaming the file to tape. Just more bytes in the buffer.

For normal restores it consults its local database because that is way faster. If you don't have the local database you do a "Catalog Tape" operation that scans the file headers on the tape to reconstruct the database. For whatever reason ARCServe couldn't complete the catalog with that specific kind of tape. Whether that was the specific version he found or was a general problem with support for those tape drives I don't know.