Re: Ah the good old days gone by...
"Any, er, retreat, on 1Mb disks? (I mean disks, not 180kb floppies! )"
Not sure about the capacity of drums in second/third generation machines. Wonder if a second generation KDF9 fixed disk was more than 1MB capacity? It had a normal set of moving heads - plus a set of fixed heads for "very fast" special data access.
The 1970 System 4 sealed fixed disk was a massive 600MB. It had two stacks of 300MB side by side. The very large head actuators were linked so they moved in opposite directions at the same time to balance the motion forces. The unit weighed 1.5tonnes and had water cooled bearings. In my mind's eye it was about 2+ metres high, 3 metres wide, and 1+metres deep. The platters were at least half a metre in diameter - and a head crash would produce a neat 25mm bright ring against the brown of the oxide. Archiving the data to magnetic tape, with a clever bit of command chaining, took 8 hours.