>I feel that I have to warn you about using tape for backup. I used it myself for many years. and felt very safe. Well, that was until I was setting up a new machine, and thought that I should start by reading in the last backup. What a disappointment that was. Although the backup system was "state of the art" with read-after-write to verify that the backup went well, I was only able to restore fragments and then it refused to continue. I tried the same with earlier backups, and the result was exactly the same. I complained, received new units, and the result was equally bad!

Had the same experience with tapes some, ahem, 30 years ago. Once a tape is bent,which could happen with those 1" big spools, they may unwind if transported, even a few steps, without the closing ring, and there's a danger that while somewhat unspooled the dangling part may crease or fold... you get the unreadable part. Now the guys from IBM knew how to skip the bad spot and then read backwards to it and lose perhaps a block or two; the guys from DEC were helpless. Once when I had to do it, I was lucky that it happened near EOT so I missed a few older versions of a few files.

The trouble with this kind of error is that it may be caused not only by a physical damage to the tape, but also by accidental magnetic discharge, fault in the material etc. There's no amount of testing that can be done without actually increasing the chances of damage. It's thin stretchable plastic and magnets, what can go wrong...

Burning it on opticals is about ten times safer, IMO, as long as the medium is not from famous bad brands ("no name" and "HP" come to mind, from my experience).

About flash drives, I had only one which stopped working, and that was some cheap thing of 4G, which was in my pocket for a number of years, then was used to hold music in the car (with extreme temperatures in the summer and then also in winter), so after about eight years it became unreliable. But at least it never got permanently lost :).