Re: Fw: [Hampshire] Replacement hard drive question

m.nuttall@??? wrote:
> Quoting Nick Chalk <nick@???>:
>> The SATA drive achieves its capacity with one
>> platter and two heads, whilst the SCSI uses
>> four platters and eight heads. That suggests to
>> me a much lower bit density on the platter,
>> which should result in better signal-to-noise
>> and less reliance on signal processing to
>> actually read or write bits.
>
> Interesting, the reviews in custom pc magazine
> suggest that less platters for a capacity means
> a higher areal? density.

True. If you have fewer platters for a given
capacity, you have to use a higher density.

> This supposively means a higher speed presumably
> because the arm doesnt have to move as much.

Higher density tends to give a higher _sustained_
data transfer rate. It doesn't do much for random
access, though.

Random access is dependent on rotation speed and
head slew rate. For rotation speed, consider the
worst case: the time for a complete rotation of
the disk if you've just missed the sector you
need. Head slew rate affects track seeks - smaller
platter diameters help there.

Nick.

--
Nick Chalk ................. once a Radio Designer
Confidence is failing to understand the problem.