They're not saying the failure rate of tapes is 50%. They're saying if you survey attempts to do data restores from tape then 50% of the time not all the requested data is found.
I can't claim the same volumes you can but I did handle tape backups and recovery for a mid sized business for a few years. We only had one tape failure in my tenure but we had plenty of failed recoveries. We had issues like the user not knowing the name and location of the missing file with enough detail to find it, or they changed the file 6 times in one day and they need version 3 and the backup system isn't that granular.
Those are just the issues after the system was set up and working well. Plenty of people set a backup system running, never check the output, and are disappointed years later to learn the initial config was wrong.
Long story short 50% failure of tapes is ludicrous but 50% failure of recovery efforts is not.
I can't claim the same volumes you can but I did handle tape backups and recovery for a mid sized business for a few years. We only had one tape failure in my tenure but we had plenty of failed recoveries. We had issues like the user not knowing the name and location of the missing file with enough detail to find it, or they changed the file 6 times in one day and they need version 3 and the backup system isn't that granular.
Those are just the issues after the system was set up and working well. Plenty of people set a backup system running, never check the output, and are disappointed years later to learn the initial config was wrong.
Long story short 50% failure of tapes is ludicrous but 50% failure of recovery efforts is not.