Can't I get a /dev/one?

[Nifty Hat Mitch]

On Mon, Jul 26, 2004 at 06:55:32PM -0400, William M. Quarles wrote:

> "Low-level" formats actually can't be done on a modern hard drive.  The
> tracks and sectors are already defined in the factory, and a true
> "low-level" format can actually damage the disk.  

This is 99% true.  Most modern hard drives do have a 'meta' command to
"go away and format yourself" (Format Unit Command).  For most vendors
this command works exactly the same as the classic controller format.
Some even permit the changing of sector size, interleave and other low
level parameters.  In some cases things like sector size changes are
virtual.  i.e. the physical format does not change but the drive acts
as if it did.

For many devices, it is also possible to discard the various defect
lists as part of this format.  For most the initial factory defect
list (generated with special hardware) is never discarded.

One interesting difference in old and modern drives is the way tracks
are placed on the disk.  Older disks could position the heads
mechanically.  Modern disks do not have the same mechanical reference
and rely on 'low level' procedures where the heads are positioned by
an external (laser) reference and media is formatted.  These magnetic
reference tracks and indexes cannot be 'reformatted' outside of the
factory process.

Modern drives have gotten so smart and complex that security folks
tear their hair out.  They know that it is possible to hide data in
spare tracks, heads, vendor tracks, and even flash memory.

Some low level commands are not published.  Some are...
Scan the web for your drive and the OEM documentation.


-- 
	T o m  M i t c h e l l 
	/dev/dull where insight begins.