🚀 go-pugleaf

For those of you who've been following the thread about low-level formatting
of hard disks check out the issue of PC Magazine which just came out.  (My
copy is at home, so I can't tell you the date.)  One of the articles 
explains why some disks (various models, various vendors) cannot be
successfully low-level formatted in the field.

As I recall this thread was started by a user who took an IBM disk, low-level
reformatted it for use on another system, and now cannot reformat the disk 
to work with the IBM controller.  The article seems almost tailor-made to
respond to that query.

In short, some disk/controllers use servo information recorded on the disk
to control the head radius and to compensate for both short-term (thermal)
and long-term (wear) drift.  Without special hardware which is unlikely to 
be anywhere but a manufacturer's facility or a large repair shop, these servo
tracks cannot be written in the field by controllers which expect to use them.
Other controllers, however, know nothing about servo tracks and cheerfully
overwrite them if instructed to do a low-level format.  The result is that
the disk, once the servo tracks are destroyed, cannot be used with a 
controller which expects those tracks to exist, and the controller is
incapable of writing those tracks even in a low-level format.

Joe Morris