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SubjectRe: disk head scheduling
On Fri, Mar 19, 1999 at 10:41:31AM -0800, David Lang wrote:
> > Well of course a 2-way elevator should sort by *ascending* sector within
> > descending track. I take it this is difficult?
> >
> > --
> Many (most? all new?) IDE drives lie to you about the real
> heads/sectors of the drive so you do not have the ability to do this
> accuratly.

Yeah, but some manufacturers are good enough to put it in the tech notes.
Should the scheduling algo be put in as a device strategy function, with
fallback to the current elevator if the device doesnt have one? Then we could
implement two way elevator algos for those hard disks for which we can get
physical geometry info from the data sheets or somewhere.

And another probably dumb question which should be answered by rtfs, but here
goes anyway:
what happens for devices like ramdisks or loopback devices etc for which
scheduling in random order is ok anyway?

-- arvind

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