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

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.