Bad sectors on HDD

Cheetah Designs · 25 Oct 2010 at 09:52

When I was in Ubuntu live CD Smart Data on my external hard drive showed there were bad sectors.

Now I have done a Full Format in Windows 7 (took hours)...can I assume those bad sectors would have been marked and the drive is now clean?

Thanks.

Philtor · 25 Oct 2010 at 10:24

Yeah a full format will mark any bad sectors and reallocate them to a different part of the disk. There's normally extra sectors on the HDD for this very purpose.

Cheetah Designs · 25 Oct 2010 at 10:31

By full format what I mean Is that I right-clicked on the drive in my computer and went to format and did a format from there (quick quick format unchecked).......that's fine right?

Philtor · 25 Oct 2010 at 10:36

Yes you have done a full format then (which takes ages as you say compared to a quick format).

CaptainCrash · 25 Oct 2010 at 14:19

philtorrens said:
Yeah a full format will mark any bad sectors and reallocate them to a different part of the disk. There's normally extra sectors on the HDD for this very purpose.

This is a bit misleading - yes, there is an area reserved for remapping bad sectors (which are present on every HDD), but it's used by the drive's firmware and on a healthy drive the whole process is invisible to the OS.

If the number of bad sectors keeps growing beyond the point where the "extra" capacity is used up, the firmware can't remap them, which is when they start becoming visible to the operating system. A full format will mark those sectors as unusable, but now it's eating into the drive's available capacity - probably not by much, at least at first, but it's normally a sign that the drive is in a bad way and there's probably more trouble ahead.