lowlevel format

[divxdude]

i bought some 20gb drives off ebay..they have bad sectors so i'm using a lowlevel format
util on them.

however its hard to tell if i'm getting improvement,

LL utils apparently zero all the data but do they map the defects on the
disk that wont hold data?

I also downloaded a util called watadiag wich offers a very detailed
map of sectors that dont provide acces in less than xx milliseconds which i like..
the goal is to map out even the slightest or problem sectors.
but its unclear if it adds those to a low level defect map.

how can i guage the success of these methods since they dont seem to discus that.

 

[CrispyFried]

well its sort of complicated. the drives are intelligent, so software on the computer cant really tell what the drive is seeing, just what the drive is reporting.

all drives have bad sectors, even new ones. bad sectors are mapped to spare sectors set aside for that use. there are two bad sector lists the drives maintain, the P-list, which are factory defects, and the G-list which is the list the drive updates as sectors go bad as you use the drive. once the G-list is full (or all spare sectors are used) you get bad sectors visible to you, and those are the bad sectors you see.

so you need manufacturer specific utils that can manage the P and G lists.

LL utils will map really bad sectors (the ones not "fixed" by the drive itself by remapping) in the FAT (or whatever the file system uses) but its not a good indicator as the drive itself will try hundreds of times to read a sector and if it can read it at all, no matter if its the 1st try or the 100th try, its seen as "good" to the LL format util. remember the drive is intelligent and software on the computer has to trust the drive, and the drive doesnt say how many tries it took to read the data, just that it was able to read it OK eventually. "slow" sectors as reported by your util are most likely on their way out.

this may not really be helpful but I figured Id try to give a little background info.

 

[Mark R]

On a formatted drive, windows will store a list of bad sectors that should be avoided. When you reformat the drive, this list of bad sectors isn't always deleted so if, for some reason Windows had mistakenly recognised a sector as bad, you won't always get that sector back after reformatting.

A true zero wipe (often incorrectly called a low level format - there's no such thing as a low level format on IDE drives) will destroy Windows' list of bad sectors - forcing it to assume that all sectors are good until proven otherwise.

The problem, however, is that all hard drives have bad sectors from the factory and will automatically work around them - they won't tell the OS about them, and you can't find out (directly) about them without a manufacturers' tool.

All hard drives also contain a significant number of spare sectors - if the drive detects a bad or weakening sector during normal use it will add that sector to the 'grown defects list' and avoid using it in future. the OS will not be informed of this, nor has any way to find out.

A complete zero wipe can help a drive work around weakening sectors by exercising every part of the disk. Rewriting every sector on the disk provides a more rigorous test than just having the drive try to read back the sector without rewriting it.

Any defects will be recorded and remapped. (Again, because this is an internal process - the OS won't be able to detect any bad or weak sectors that were found. A SMART tool, or manufacturers' tool may be able to tell you how many sectors have been added to the defect list).

If you've done a full zero wipe, but when you reformat you get bad sectors detected, then this is a sign that the drive has suffered severe damage because there are so many defects on the disks that the drive has run out of spare sectors, or space in its defect list.

The bad sectors that you are seeing after zero filling are just the tip of the iceberg - the true extent of the damage remains hidden inside the drive.