Check disk

Devilsbane

When you run chekdsk /r or you check the box "scan for and attempt to recovery of bad sectors" does it mark the sector as bad.

I was told previously that the only way to mark a sector as bad was to do a full format (not a quick) and that using check disk with this option would attempt to recover data for the sector, but it couldn't mark it as bad so data could get stored there again. I'm watching a CBT nugget, and they say that this option will mark the sector as bad and then never save data to it again.

So which is it? Bonus points for providing a link. I really wanted to find something published from MS on this, but couldn't turn anything up myself.

Thanks

bdub

Looks like CBT Nuggets is right according to this (or wrong depending on how you look at it). Cannot Create Software Mirror If Disk Contains Bad Blocks

Its the difference between marking the bad sectors at the file system level (chkdsk) or the hardware level (format).

Devilsbane

So chkdsk marks the sectors as bad, but then still allows data to be saved there?

Or is that just because this article is for a mirrored volume?

bdub

Yeah its talking about software mirror. So its saying that normally chkdsk will mark bad sectors and so windows would normally not write information to any bad sectors that have been marked by chkdsk. But that when creating or adding a mirror you might receive the error stated due to bad sectors, in which case you would need to low level format the drive to mark bad sectors at the hardware level. Obviously having the bad sectors marked at the hardware level is better, but for most purposes its not necessary.

To clarify it a little bit more, chkdsk will tell the file system (usually NTFS) "don't write any information to these sectors" effectively telling Windows that those are bad sectors. However, in the case with creating or adding a software mirror it copies all sectors completely disregarding anything that has to do with the file system on that drive.

My guess is this is one of the reasons why hardware RAID is better than software RAID as you would typically be formatting the drives using the hardware RAID controller which would mark any bad sectors at the hardware level.