> On Sep 28, 2017, at 12:04 PM, Jon Elson via cctalk <cctalk@classiccmp.org>
> wrote:
>
> On 09/28/2017 10:31 AM, Chuck Guzis via cctalk wrote:
>> And even the sector size on recent drives is fictitious. Larger drives use
>> 4K sectors but "translate" them to the 512 byte standard.
> So, for every write, it needs to read the 4K sector, alter the bytes and then
> rewrite it? Hmmm, explains why writes are slower than reads even on spinning
> disks. Of course, if you write entire tracks, it can just hold the partial
> data until it has all the data for that track, and write out the buffer in
> one rotation.
Yes, "512 emulation" drives are a performance problem and I don't trust the
firmware either. It's a whole lot more complex than a regular disk drive. If
you have 4k physical sectors, the better answer is to use 4k sectors natively.
Current OS versions have no problem with this. That way you avoid hairy and
slow drive firmware.
On geometry, it's quite some time ago that drive designers reinvented
non-uniform track lengths. CDC did this way back in the early 1960s, but then
for a long time sector counts tended to be the same on all tracks. CDs changed
that, and hard drives started doing so also. As a result, the C/H/S values you
get from a drive are unavoidably a fiction, because even if the designers were
willing to give you the real number, they couldn't possibly do so because there
isn't a single answer.
paul
