On Tue, Oct 4, 2011 at 8:59 AM, Tina K. <[email protected]> wrote: > If you zero out a hard drive with Disk Utility to map out the bad blocks, > are they notated in a permanent fashion or will a simple reformat lose the > bad block "map."
As Peter said, current drives remap bad sectors automagically in their firmware. My understanding is it works this way. If the drive attempts to read a sector and the read fails, the sector is marked as "pending". It is not remapped under the rational that the read may succeed in the future. So if you see a non-zero value for pending sectors in the drive's SMART data, this is what has happened. If you write to a sector and the write fails THEN the sector is remapped (if possible). This is tallied in the Reallocated Sectors Count, I think. The drives firmware keeps track of the remapping and reads/writes to that sector redirected from that point on to the remapped sector. The gist is that if you have bad sectors and you want to force the drive to remap them you have to write to those sectors. One way to do this is to perform an erase of the drive i.e. write zeros (or whatever) to every sector on the drive. A format in and of itself may do nothing. It all depends on what sectors on the drive the format writes to. FWIW, I'm not sure what the phrase "low level format" means with any drive sold this century. For quite some time the format of a hard drive is fixed once it leaves the factory and this can't be tinkered with other than remapping bad sectors via the firmware. And, yes, if you have a large number of either pending or reallocated sectors on a drive, it is a cause for concern about the health of the drive. Especially if the number keeps going up. -irrational john -- You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list
