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
