On Fri, 17 Dec 1999 01:51:54 +0200 (IST), Evgeny Stambulchik
<[EMAIL PROTECTED]> wrote:
>As far as performance is considered, it's not RPM that usually matters (inspite
>of a big hype), but the amount of cache on disk. Until recently (1-2 years), the
>maximum cache on IDE disks was 128KB, while about each SCSI disk had 0.5MB.
I would speculate that all the on-disk cache you need is two full cylinder's
worth of data.
You want at least one cylinder's worth of data so you can read it all in one
round, and really want two so you can read the next one while your buffers are
still being transferred to the PC.
I have a hunch that with a computer fast enough, anything over 2 cylinder's
worth of data will offer near zero improvement. After all, the system cache is
more efficient than going to the drive and pulling data from the HD cache, so
the HD cache can only help you if it lets you stream the data at the maximum
possible speed (one rotation for each full cylinder).
The problem is that it's hard for us customers to really estimate how much
cache is really in these drives (in terms of number of cylinders), since the
numbers of cylinders pronted on the disk label has nothing to do with the
actual number of physical cylinders it has.
>Regards,
>
>Evgeny
Udi
ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ
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