Can't I get a /dev/one?

[Benjamin J. Weiss]

On Thu, 15 Jul 2004, William M. Quarles wrote:
> James Wilkinson wrote:
> > You might not be aware of this:
> > 
> > Modern hard disk drives keep a number of sectors spare. When a sector
> > fails (or is failing), and the computer attempts to write to that sector,
> > the hard drive will automatically use one of its spare sectors instead.
> > Any further references to that sector will automatically be rerouted to
> > the new, good location.
> > 
> > This is all done internally by the drive: the OS typically never even
> > sees this.
> > 
> > It sounds like you've already written zeros to the entire drive. This
> > would have replaced all the bad blocks already: you *shouldn't* see any
> > bad blocks.
> 
> I was partially aware of this.
> 
> In M$ OSes, I've also seen disks get bad sectors detected on them, then 
> when they are fully (or mediumly) reformatted, the bad sectors 
> disappear.  Is this a necessary step to get the drive to make use of 
> those spare sectors?

I believe that this is what is called a "low level" format.  IIRC, it 
formats all of the sectors, both good and bad and resets the flags.  Then 
it reserves a bunch of sectors as spares.  Then it tests all of the 
sectors to see if they'll hold the data properly.  If the software detects 
a problem, it flags the bad sector and brings a spare into use, just as 
James said.

Ben