Re: "Repair" hard disk with bad sectors by reading and rewriting same data?

On 8/14/20 4:44 PM, VanguardLH wrote:
> VanguardLH <[email protected]> wrote:
> 
>> Seagate has their own SeaTools you might try.  Make a bootable CD from
>> which to run their software.  That way, the bad HDD is quiescent, and it
>> doesn't matter what OS is there.  Any remapping is done at the hardware
>> level, not at the OS level in whatever file system the OS uses.
>>
>> https://www.seagate.com/support/downloads/seatools/
>> Get the bootable version.  Then you don't have to install it in any OS,
>> and you don't have to move the HDD between computers.
> 
> I found:
> 
> https://www.hdsentinel.com/usbboot.php
> 
> I'm guessing it uses an image of their free DOS edition mentioned at:
> 
> https://www.hdsentinel.com/hard_disk_sentinel_dos.php
> 
> I still don't see in its description that it does any testing to prod
> the HHD's firmware to remap the bad sectors.  Seems to be just for
> analysis.  The Seatools might just be a diagnostic tools, too.
> 
> I'm surprised smartctl didn't get remapped the bad sectors/blocks.  Bad
> blocks is one of its functions.  If there are no spare sectors reserved
> for remapping, then there's no way to remap any more bad sectors.
> 
> There is no information in SMART or by reading an HDD's firmware
> signature to know the size of the pdata table.  The p-list table is the
> remapping done at the factory.  g-list (growth list) is used for further
> remapping during the use of the drive.  I've seen where there was a jump
> in bad sectors that got remapped (pending count went up, and then fell
> to zero), and it could be a couple hundred sectors; however, without
> knowing the total size of the g-list table (to know how many spare
> sectors are available), there is no way to know how much is left.  The
> drive makers don't publish the size of their g-list table.  200 bad
> sectors is really bad if there are only 400 spare sectors total for
> remapping, but not immediately serious if there are 20,000 spare
> sectors.  Bad sectors tend to grow radially on spinning magnetic media,
> so if some show up then it becomes more likely that more will show up.
> You cannot know severity of a remap event when the total or remaining
> capacity isn't known.
> 
> But if the HDD's firmware doesn't remap the bad sectors, that could be
> because there are no more spare sectors.
> 
> https://dtidatarecovery.com/how-to-fix-bad-sectors-on-a-hard-drive/
> "Since we know that all bad sectors are remapped to a pool of unused
> sectors, and the size of this pool is substantial, the only way a bad
> sector will show up on your system is if the pool has been completely
> used. In other words, your remapping pool is so full that it cannot take
> another bad sector and now the drive is throwing errors that it can’t
> read from a sector."
> 
> Start checking on prices for replacement HDDs of equal, or greater,
> capacity to which you can clone the old HDD.  If possible, see if you
> can determine in which files are the bad sectors.  The clone software
> should keep a long, too, to let you know if there were read errors from
> the old drive.  If they are data files, you can recover those from your
> backups.  If they are program files, well, you could uninstall and
> reinstall the programs to ensure all their bits are correct.  If the bad
> sectors are in system/OS files (which rarely get rewritten except by
> updates, and then only some of the OS files get replaced), well, you'll
> have to see if the cloned HDD is bootable, the OS behaves, and you
> experience no problems, or reinstall the OS on the new HDD, reinstall
> all the apps, and restore the data files to it.  If your backups include
> full-partition images, you can obviously not bother with the clone
> operating and just restore the backup image to the new drive.
> 
> If the pending count doesn't go down, you have a drive that won't heal.


The Pending Count alwsys does go to zero after writing zeroes to the 
whole drive.

Perce