Electronics > Repair

HDD bad sector repair software?

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magic:

--- Quote from: Whales on October 01, 2024, 03:57:10 pm ---This means that if a modern drive is reporting bad sectors: something VERY bad is happening.  So bad that it has run out of space sectors, which almost always means you have an accelerating problem of many more bad sectors than you can see.  A drive will only report errors to the OS if it has run out of options.

--- End quote ---
No. Getting read errors and seeing non-zero "Current Pending Sectors" simply means that there are unreadable sectors which the drive will not touch until you overwrite them, because there is always chance that a future read may recover them successfully.

Whales:
I'll also add that software claiming to "repair" bad sectors has always been dubious.

When a drive writes a sector (which might be 512bytes, 4096bytes or sometimes secretly larger in modern SSDs) it actually writes more than that number of bits physically to disk.  Eg it might write 600 bytes for a 512byte sector, but don't quote me on the exact numbers.  This gives it the ability to add error-correcting codes.  A few bits can go bad, but the sector's data is then still fully recoverable.

This is 100% necessary because even normal reads and writes will lead to bad bits on modern SSDs and HDDs.  There are pushing their mediums right to the limit of density, bitflips are common, but error correcting codes make this manageable.

When a bad sector is encountered they might move it elsewhere or perhaps even keep it in the same spot (if the errors are minor or disappear if read a few more times), the exact algorithms are at the discretion of the drive maker.  As long as they can guarantee no data loss for the warranty period they are keeping up their end of the deal.

If a sector has so many failed bits that the error correcting code is useless, then there is nothing the drive can do to get your data back.  At this point it reports a failed read to the OS.  Your data is lost permanently.  There is nothing that third party software can do here that the drive firmware has not already tried (and with much better insight into the disk's low level layout).

This failed sector is only bad transiently.  If you write to it then the drive silently handles relocating it elsewhere or similar.  It should not stay broken after being written to, unless something is horribly wrong with the drive.

If the drive is reporting lots of bad sectors then shit has hit the fan.  Its error correcting codes are failing everywhere, it can't see a clean view of its own platters/flash/media and its whole worldview is falling apart.

Whales:

--- Quote from: magic on October 01, 2024, 04:08:45 pm ---
--- Quote from: Whales on October 01, 2024, 03:57:10 pm ---This means that if a modern drive is reporting bad sectors: something VERY bad is happening.  So bad that it has run out of space sectors, which almost always means you have an accelerating problem of many more bad sectors than you can see.  A drive will only report errors to the OS if it has run out of options.

--- End quote ---
No. Getting read errors and seeing non-zero "Current Pending Sectors" simply means that there are unreadable sectors which the drive will not touch until you overwrite them, because there is always chance that a future read may recover them successfully.

--- End quote ---

(bold emphasis mine)

EDIT: I"m talking about read errors that make it to the OS, not read errors that are silently and internally fixed by the drive.

That's still very bad.  A read error making it to your OS means the drive has already tried several times and given up.  If those bits are part of your OS or software then you will see crashes; and if part of your files then broken files.  All guarantees from modern software are thrown in the bin the moment any part of their data is unreadable.

There are some types of drives that are tweaked to give up very easily (surveillance disks, where delays from retrying are worse then accepting a few failed operations); but for everything else you should treat read errors that make it to your OS as "something VERY bad is happening".

fzabkar:

--- Quote from: Retep on October 01, 2024, 02:27:11 pm ---There is a product called "SpinRite" (https://www.grc.com/sr/spinrite.htm) which makes some claims in this area. It could very well be snake oil; I've no personal experience with this product.
--- End quote ---

If you value your data, stay away from this prehistoric pile of excreta.

Deconstructing SpinRite:
https://www.hddoracle.com/viewtopic.php?f=36&t=2929

magic:

--- Quote from: Whales on October 01, 2024, 04:09:58 pm ---If a sector has so many failed bits that the error correcting code is useless, then there is nothing the drive can do to get your data back.  At this point it reports a failed read to the OS.  Your data is lost permanently.  There is nothing that third party software can do here that the drive firmware has not already tried (and with much better insight into the disk's low level layout).
--- End quote ---
If you care about the data, there is software which will keep retrying (even for weeks) and it helps in some cases.


--- Quote from: Whales on October 01, 2024, 04:14:04 pm ---There are some types of drives that are tweaked to give up very easily (surveillance disks, where delays from retrying are worse then accepting a few failed operations); but for everything else you should treat read errors that make it to your OS as "something VERY bad is happening".

--- End quote ---
Obviously it's bad, but it doesn't mean that the disk has run out of spare sectors. Nor does it necessarily mean that it's a write-off in every case, sometimes there are cost vs reliability tradeoffs to be made and sometimes the cheap option works out OK.

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