Another WTF moment

[Ronald F. Guilmette]

In message <CAJ-VmokfpSKqzmYiPhdy53kViXtWuUV8TeGpuY6rkJthdirXVQ at mail.gmail.com>
Adrian Chadd <adrian at freebsd.org> wrote:

>Wow, I didn't even know this existed!

My apologies for not replying sooner.  It has been a hectic few days.

Anyway, yes, there are two kinds of "hidden" areas that may be present
on a hard drive, Host Protected Area (HPA) and then separately also
the Device Configuration Overlay (DCO).  To be honest, I only found
out about these myself a couple of months ago as I was researching the
proper way of _completely_ eraseing drives prior to disposal.  (Hint:
Search out a program called "HDDErase".  It clobbers _everything_,
including even these two hiddfen areas.)

>Would you mind filing a doc PR with this information, along with how
>you figured out it was a HPA?

Ummm... I'm not sure.  I only fill out PRs when I see some specific
FreeBSD document that I _know_ is either incorrect or incomplete in
some way.  I am not immediately aware of what specific FreeBSD document
either can or should document this particular somewhat obscure aspect
of modern hard disk drives.  I mean it is just an obscure hardware
feature, not unlike the specialized codes that might be transmitted
by pressing button #7 on your 10 button "gamer" mouse.  I don't think
it is incumbant upon FreeBSD to document all such obscure things.

As regards to how I verified my suspicion that the size discrepancy 
might be due to the presence of an HPA on one of the drives, the
following page shows exactly how to do that.  (Too bad that it assumes
that you have booted to some flavor of Linux, but oh well.  There
are plenty of LiveCD versions of Linux out there which one can boot
from, when & if one needs to check for the presence of an HPA.)

http://www.forensicswiki.org/wiki/DCO_and_HPA

>I'm sure this is going to come up from time to time and it'd be great
>if someone would take the doc PR and turn it into a FAQ entry.

Someone?  Are you volunteering?


Regards,
rfg