50th Anniversary of invention of disk drives 4589

360 had fixed head 2303 & 2301 drums (2301 effectively a 2303 but read-write four heads in parallel) and 4mbytes capacity in the era of 2311 (7mbytes) and 2314 (29mbytes) disks.

in the early 70s with 370 came 3330-1 (100 mybytes) and then 3330-11 (200 mbytes) and the fixed-head disk 2305 (12mbytes) was replacement for 2301-2303 drums.

after that, electronic store was becaming plentiful enuf to start doing caching (somewhat mitigating requirement for fixed head disks).

when cp67 originally showed up at the univ. its disk i-o strategy was strictly FIFO and paging operations were done with a different-unique i-o operation per 4k page transfer.

one of the performance changes i did as an undergradudate at the univ. was put in ordered arm seek queueing ... and where possible whould (try and optimally) chain all queued page transfers into single i-o (for the same device on drums and for same cylinder on disk).

the ordered arm seek queueing allowed at least 50percent better thruput under nominal conditions and system degraded much more gracefully under heavy load.

the single page transfer per physical i-o would peek around 80 page transfer per second on 2301 drum (avg. rotational delay for each page). which chaining, a 2301 would peak around 300 page transfers per second.

later i did page mapped interface for the cms filesystem in which i could do all sorts of fancy i-o optimizations (that was a lot more difficult and-or not possible using the standard i-o interface paradigm). post this year about some performance stuff with paged mapped interface

misc. posts mentioning paged mapped interface work

various past postings mentioning 2301s and-or 2305s