http://www.gizmodo.com/archives/woul...lly-018574.php
The picture is of a fixed-head disk, very similar to a Borroughs unit I had the pleasure of disassembling (in 1975) after a catastrophic head crash (I got authorization from Gordon Bell himself to do it). It took me 3 days to whittle it down to nuts and bolts, and the platter weighed 18 pounds. The hub upon which the platter was mounted was phosphor bronze, and weighed an additional 17 pounds.


It held a few megabytes at most, if I recall correctly (a similar unit was used as a swap disk on the PDP-10, so it would have held 256K or so)