Rama,

That's interesting. I assume these HDs contained large Host Protected Areas. These areas can be removed even from empty HDs to recover the full HD size. Tools that can be used are...

Hitachi Feature Tool
MHDD
HDAT2

Dell laptops formerly used a HPA of a few GB for MediaDirect2. Just removing the HPA wasn't enough. You had to zero LBA-3 as well, otherwise the HPA would be recreated at the next boot.

On a related theme, the article Hard Disk Sector Structures explains that a disk sector "actually holds much more than 512 bytes of information.  Additional bytes are needed for control structures, information necessary to manage the drive, locate data and perform other functions."

What else do the forum members know about these "control structures"?  I have been unable to find any more details on the Seagate website or elsewhere.

Pleonasm wrote on Aug 19^th, 2007 at 10:03am:

He's more talking there about the classic on-disk layout used by disk controllers in the MFM days, when the on-disk layout was pretty much a simple one-to-one mapping with what you told the controller and you needed to be reasonably aware of the sync/address/gap fields. Folks worrying about sector interleaves was another product of this era.

I don't think I still have any of my 1970's disk controller chip manuals to point you at (if I do, they are buried in the stacks) but they explained the low-level formatting process in some detail. By the time the PC arrived the disk controller chips had taken more of this process on themselves during low-level track formatting so you want to refer to hardware more primitive than that (or else look at the group-code recording used by the Apple ][ and Amiga, since it's roughly similar).

However, the sheer number of layers of interface abstraction present these days means that you really can't talk about those kinds of structures any more - to the extent they even still do exist, you can't get at them. And that's a good thing, mostly.