Re: Benefits from computing physical IDE disk geometry?

[John Bradford]

> Any good SCSI drive knows the physical geometry of the disk and can
> therefore optimally schedule reads and writes.  Although necessary features,
> like read queueing, are also available in the current SATA spec, I'm not
> sure most drives will implement it, at least not very well.
> 
> So, what if one were to write a program which would perform a bunch of
> seek-time tests to estimate an IDE disk's physical geometry?  It could then
> make that information available to the kernel to use to reorder accesses
> more optimally.  Additionally, discrepancies from expected seek times could
> be logged in the kernel and used to further improve efficiency over time.

On a system that's been set up with one large root partition, and
nothing else, you might get a noticable gain, but I would guess that
you could get a simliar gain by partitioning the disk and manually
placing, E.G. /var near the outside of the disk, and things like /etc
near the centre.  I.E. placing more active partitions on faster areas
of the disk.

> If it were good enough, many of the advantages of using SCSI disks would
> become less significant.

Not really - there are still a lot of advantages of SCSI that it
wouldn't address.

John.