This was the approach IBM used in it's first RAMAC RAID where I think they had 
to buffer a whole cylinder but that was many generations ago

(my copy of the specs may not be exact):
Buffering a whole cylinder, or a whole surface, of the RAMAC was no big deal.
One hundred surfaces (52 platters, but not using bottom of bottommost nor top 
of topmost) totalling to 5 million 6 bit characters.
That's 50,000 characters per surface.
OR 50,000 characters per cylinder
("square geometry" :-)

On Fri, 15 Apr 2022, Paul Koning wrote:
"Was" as in "back in the day"? 50k characters would have been quiet a large memory in the 1950s. And for an I/O device, any kind of buffer is not necessarily all that useful.

50K would be bordering on extreme in the 1950s, and considered a LARGE buffer through the 1970s. Certainly wasn't practical with less than 16 bits of addressing.



What does make sense is a track buffer in drum memory machines, as found for example in the Dutch ARMAC, where the first implementation of the famous "shortest path" algorithm was first implemented.

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