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No, I said cassettes. And I immediately drew a distinction between them and tape cartridges engineered for data storage.

OK: I misunderstood what you meant.

I think I have had (bad) experience with the cassettes you meant. They were 4mm for a Hewlett-Packard C1539A DDS-2 tape drive. It was so unreliable that the computer manufacturer sent me a new one under warranty to replace it. It was no better. So the manufacturer asked if I would consider a VXA-1 (the only model available at the time) and after looking it up on the Internet, I agreed. They were $1000 each at the time, but the manufacturer of the computer agreed to eat the cost. They said they had so much trouble with the HP drives that they no longer offered the HP drive with their machines. The best feature of that HP drive was you could stick a backup tape in there, and by pressing the right buttons when booting the computer, you could do a "bare metal" restore. I.e., you could buy a new machine with no software in it except for the BIOS, and restore your previous system on it if it had the same architecture and enough disk space. But the thing was so unreliable that I never tried that.

Frankly, I am amazed that drives like that work at all. They use 4mm tapes and record something like 64 tracks on them. So when recording, it writes one track from one end to the other. Then it moves the head down the tape by 1/64 of a millimeter and writes the next track in the other direction, etc. Well those tapes just do not have the tracking ability to do that. Furthermore they must be written at a constant speed or the tape skews differently at different speeds. I imagine it would never be possible to read one of those tapes written on one drive on another. And the drives are nowhere near heavy enough to use as an anchor for small boats.

The VXA drives are helical scan, and they normally write at full speed if the computer can keep up. Normally, it can because mine all have SCSI interfaces and a SCSI controller can normally keep up, especially with a fast machine. But one feature of the VXA drive is that it does have a data buffer and if the computer is not keeping up, it slows down the tape speed so it does not get ahead of the computer. If necessary, it can even stop the tape. When that happens, it does not need to back up, go forward, get up to speed and then start writing again. The HP drive did that all the time. Someone called it shoe-shining. Not a good thing. Drives like that gave tape a bad name.
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