** This is the quasi-official and semi-temporary T13 email list server. **
On Mon, 21 May 2001 09:42:08 +0200, [EMAIL PROTECTED]
wrote:
>I can assure you that it is possible to extract head skew, cylinder
>skew, sectors per track, zone tables for ATA IDE drives using standard
>data commands. This is much easier when the drive supports the
>disabling of read and write caching, but not essential.
Why don't you just ask the drive manufacturer for this information?
Or don't you trust them? Or don't you like the NDA they hand you to
sign?
My guess is you are measuring things and getting numbers that "look
right" to you but probably are not anything like what the real drive
is doing.
>It seems from your answer that you have never performed such measurements.
>I am quite surprised at this, knowing your experience.
I don't do these kinds of tests because I know they are a waste of
time, extrememly inaccurate and provide no valid information.
>Although, we do not characterise a drive family, but a drive. General
>design rules are fixed for a drive famliy such as formatting, firmware
>etc. When purchasing HDD's in large numbers, of course we would expect
>to be informed of major changes.
If you are really testing only one drive, then you really are getting
worthless numbers. Again why go to all this trouble? Why do just ask
the drive manufacturer for the information?
>I agree with you that each drive is different, due to factory found
>defects and grown defects. Note, however that these can also be
>detected, so we do have an idea, which I believe is your next point.
What about drives that map out an entire zone under one head because
there are too many defects in that zone? The next drive you test may
have a different zone or head mapped out. What is it that you think
you are measuring?
>We measure the complete seek curve as a function of seek distance
>and yes sometimes strange servo code based effects appear, but that
>is exactly what we are checking for. We want predictable HDD's
Please explain what you mean by predictable... Are you testing one
drive and then tweaking your host software with that information and
expecting all drives of that brand and model to work the same way?
>We can extract enough information from command timing to model
>the HDD based on what you would term a physical LBA mapping.
Can you explain all the different schemes that are used by various
drives to layout sectors across the zones and heads? I can think of
at least five schemes and I seriously doubt you can detect them by
sending read/write commands to a drive!
>Again, this can be extracted from command timing. We do this, so
>please do not say it is impossible. It has been confirmed against
>information supplied by HDD vendors for a number of drives.
OK, you said it, you do not trust the drive manufactuers. I guess not
much more needs be said.
*** Hale Landis *** [EMAIL PROTECTED] ***
*** Niwot, CO USA *** www.ata-atapi.com ***
--
If you have any questions or wish to unsubscribe send a
message to Hale Landis, [EMAIL PROTECTED] To post to
this list server send your message to [EMAIL PROTECTED]
For questions concerning Thistle Grove Industries or TGI's
list services please send email to [EMAIL PROTECTED]
