Magnetic tape filesystem

Chuck Guzis cclist at
Sun Feb 8 20:02:16 CST 2015

Disks and drums were a luxury on old systems; there were many versions 
of tape-only operating system.  Even S/360 had TOS.

Anyone know of a port of IBSYS or FMS to  modern gear?

One of the problems of using tape as a working medium is that, with a 
few exceptions, rewriting of data in place can be problematical. (with 
tape speed variations, you aren't guaranteed that overwriting a block on 
tape will occupy the same amount of tape as the old one.

So you're essentially limited to skipping to a filemark, then creating a 
new end of information by writing after that.

However, many mainframe systems automatically archived inactive files to 
tape, retrieving them back to disk when requested.  There were tape 
robots for regular 10.5" reels, as well as interesting mechanisms for 
storing data on special tapes, e.g. IBM 3850, 2321.

Archive and a few other PC QIC-based systems allowed for block overwrite 
and could simulate a disk, albeit pretty slowly.

And then there's the Exatron Stringy Floppy.


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