General recovery of harddisk question

I know the theory but at least one major manufacturer, Western Digital, thought that it was worth implementing what they called "wear levelling" whereby the heads were moved ever 15 seconds when the drive was not being accessed so that each track took its share of "wear".

If the read/write heads never touch the drive surface (as described in WD's own literature) then I think this can be taken as the marketing bull sh!t that it appears to be.

Although I have to agree with the 'theory' my experience of recovering data from failing disks, often shows the error rate increases in the directory area. In my (maybe limited view) it is worst on Apple 2.5" disks.

An apple directory block is often 8 or 16 sectors long, with pointers at front and back. It may store maybe 40 file names and so the whole block could end up being rewritten everytime a single file is changed. Possibly 40 times more frequently than an NTFS MFT entry.

Does constant reading and writing possibly cause heating problems??

I read once that no program is available that would write over (wipe) bad sectors, so how's this possible to do?

I read once that no program is available that would write over (wipe) bad sectors, so how's this possible to do?

The ATA specification calls for special commands that are executed within the drive that will wipe all the data area. These are not generally available to the user but there is software that will invoke these commands.

I read once that no program is available that would write over (wipe) bad sectors, so how's this possible to do?

The ATA specification calls for special commands that are executed within the drive that will wipe all the data area. These are not generally available to the user but there is software that will invoke these commands.

Something like this http//cmrr.ucsd.edu/people/Hughes/SecureErase.shtml

wipes HPA and/or DCO areas

I read once that no program is available that would write over (wipe) bad sectors, so how's this possible to do?

I wrote the first commercial program that could do this back in about 2002.

http//www.sandersonforensics.com/old%20html%20stuff/manual.htm

If you used the inner Erase function of the ATA/SATA, all drive sectors, included those mapped as bad will be re-written, thus you need to have both the chance of the compromising data being on one of those very few sectors AND the internal 00 writing completely failing.jaclaz

The OP had specified the erasing software as dban PRNG stream, this does not use the ATA erase function. However "The current ATA specification for Normal Erase mode states that the SECURITY ERASE UNIT command shall write binary zeroes to all user accessible data areas. (ATA reassigned blocks are not user accessible because they have no user address)."

There is an Enhanced Erase Mode that will get the re-mapped sectors.

Yep. )
I was meaning

If, instead of using DBAN, you used the internal ATA/SATA function….

referring to my post on the "Singler pass wipe" thread, which was referenced by mscotgrove, which quotes the docs about "Secure Erase" from
http//cmrr.ucsd.edu/people/Hughes/SecureErase.shtml

jaclaz