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SubjectRe: [OFFTOPIC] Re: disk head scheduling
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"Richard B. Johnson" <root@chaos.analogic.com> writes:

> This means that read amplifiers that used to handle data at up
> to 10 MHz are now handling data at 800 Mhz to 1 GHz. You can
> check the numbers yourself. The bits per second that travel under
> the read head is now much greater than the bits per second that
> any I/O interface can handle. This means that sector interleave,
> spiral compensation, and other tricks are now worthless because
> nothing you do along these lines will allow you to actually use
> data as fast as it becomes available. The data just arrives too
> fast. Because of this, sectors are no longer interleaved.

Could you provide a reference to support those transfer rates - the
Quantum Atlas III which looks fairly modern is specified as having
internal transfer rates between 110 and 180 Mega bits per second (see
http://www.quantum.com/products/hdd/atlas_III/specs.html), IBM's
Ultrastar 36XP 3.5 is specified at 143.2 to 231.2 Mbits/sec (see
http://www.storage.ibm.com/hardsoft/diskdrdl/ultra/36xpdata.htm) and
the best Seagate drives top out around 264Mb/s - these are comfortbly
less than current SCSI transfer rates of 80MB/s(= 640 Mb/s) which are
themselves are easily accomodated by a 32bit, 33MB/s PCI bus (and
Fibre channel is even faster) so I'd say the interfaces are still
faster than the physical media.

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