4 ms·

"No HDD on the market has ever been variable-speed." I'm not sure that's true ... I remember from one of the Sun Performance Tuning manuals there is a chapter

by rsync 5y ago

"No HDD on the market has ever been variable-speed." I'm not sure that's true ... I remember from one of the Sun Performance Tuning manuals there is a chapter on disk performance and there was a throwaway line about "non commodity disks". Specifically, that there were, in the past, disk drives with heads that moved independently. I don't know much more about "non commodity disks" - I think they must have been prevalent in the 70s (?) - but variable speed doesn't sound much weirder than independent head movement ...

rzzzt 5y ago
Dual head stacks were once a thing, and there was a recent thread about them as well: https://news.ycombinator.com/item?id=26502216 https://news.ycombinator.com/item?id=26502216
userbinator 5y ago
Multiple heads moving independently have many advantages, varying the spindle speed doesn't; it takes a lot of energy to change the speed of the platters, and doesn't really provide any benefits. Zoned bit recording already takes advantage of the varying linear density, and doesn't require changing the platter speed. In the 70s, disk drive motors would likely be mains powered synchronous induction motors, which are constant speed and where the traditional speeds of 3600, 5400, and 7200 originated.
wmf 5y ago
I've only heard about one model of dynamic RPM (DRPM) hard disk and only prototypes were made.
bradknowles 5y ago
Sony 3.5” floppy disks used to be variable speed. I knew about that at the time I interviewed for a position as an intern at Imprimis in 1989, just before they got bought by Seagate. The guy I was interviewing with smiled smugly and said “we’ve got a better solution — we vary the speed at which we read and write data!” As a result of that job, I ended up writing what I believe to be the first FAQ for hard drives and stiction — in 1989. I haven’t been able to find a copy of it, however. Dunno if there would be any useful information in that FAQ for the OP, but it would be interesting to check it out and see. That is, if anyone can find a copy.

by rsync 5y ago

rzzzt 5y ago

Dual head stacks were once a thing, and there was a recent thread about them as well: https://news.ycombinator.com/item?id=26502216 https://news.ycombinator.com/item?id=26502216

userbinator 5y ago

Multiple heads moving independently have many advantages, varying the spindle speed doesn't; it takes a lot of energy to change the speed of the platters, and doesn't really provide any benefits. Zoned bit recording already takes advantage of the varying linear density, and doesn't require changing the platter speed. In the 70s, disk drive motors would likely be mains powered synchronous induction motors, which are constant speed and where the traditional speeds of 3600, 5400, and 7200 originated.

wmf 5y ago

I've only heard about one model of dynamic RPM (DRPM) hard disk and only prototypes were made.

bradknowles 5y ago

Sony 3.5” floppy disks used to be variable speed. I knew about that at the time I interviewed for a position as an intern at Imprimis in 1989, just before they got bought by Seagate. The guy I was interviewing with smiled smugly and said “we’ve got a better solution — we vary the speed at which we read and write data!” As a result of that job, I ended up writing what I believe to be the first FAQ for hard drives and stiction — in 1989. I haven’t been able to find a copy of it, however. Dunno if there would be any useful information in that FAQ for the OP, but it would be interesting to check it out and see. That is, if anyone can find a copy.