View Full Version : Bad sector detection and recovery/remapping

The Error Guy
30-03-2013, 12:08 PM
My laptop HDD (unsurprisingly - since it gets a lot of use and is moved around a lot) has a few bad sectors, no performance degradation and it runs ok so I'm just keeping my data backed up and I'll wait till it eventually gives up the ghost on me or gets too messy to use.

My WD external HDD has also developed a few bad sectors, however recently performance has just completely died out on it. I forget the exact numbers from the SMART status but HD Tune has it on "warning" so I'm guessing it's not too bad. Anyway, copying to/from the drive is dicey, it will start out at 60-100MB/s then hang at about 30MB/s but won't actually be read/writing any data (the file transfer just stalls - on OSX it gives that lovely ambiguous error -36 after a few mins). When scanning with HD Tune the first 650GB are fine (it's a 1TB drive), after that it hits a few bad sectors and the error scan slows to about 0.1MB/s (it was so tediously slow and I needed my laptop, so I stopped the scan there)

I'm guessing these bad sectors are what's giving this drive some grief, so I was wondering what's the best way to clean up these sectors or re map them. Obviously if they are physically damaged there's not much I can do, but I'm hoping they are CRC/soft errors which I can re map until I can reformat the HDD (which should fix the sectors if they're just caused by invalid CRC) I have had a google around but most searches just bring back no hopers trying to fix physical bad sectors or saying to use windows built in error check (unless that's the best thing to use).

I'm also slightly suspect of the WD Sata/USB interface, but I can't test the drive without it. WD have this weird thing going on with their gear where if I plug a different drive into the WD USB controller It won't show up (partition manager reports it as uninitialized) and if I plug the WD drive into a different USB controller the WD drive will show up uninitialized. The WD 1TB drive will only work with the WD USB 3 controller. I should probably post on the WD forum about that or see if I can find a solution because it's really annoying. (side thought - Does it in Win8/7, havn't tested it with mac/Linux, it could be windows packing a sad for some reason)

Anyway, back to the original question, assuming that the USB/Sata interface isn't at fault, what's the best software to scan for and attempt to recover bad sectors or re map them if possible?

Any educated light to be shed on the topic would be much appreciated :)



30-03-2013, 02:34 PM
Generally when they start developing bad sectors it's time to replace them or send them back under warranty. That said if you want to persevere (making sure everything is backed up of course) and see if they can be recovered you should start with the manufacturers tools from their website. They are not consistent with the name of the function but you want to do the equivalent of a Zero fill or low level format which will wipe the drive and remap bad sectors to the hidden pool they keep in reserve. While it's not generally worth the effort drives do sometimes develop a few bad sectors and remain otherwise ok, in those (rare) circumstances a zero fill can completely hide the problem.

I had a drive with a bad sector caused by a software fault that left it writing to the same sector for about 8 hours, after zero filling it ran fine for several more years. Curiously seatools quick diagnostic would always flag it as faulty after that but the long diagnostic test would pass 100%. I guess there is still a flag somewhere to say there are bad sectors on the drive even when they are hidden.

Another trick from many moons ago is if the bad sectors just happen to be at one "end" of the drive (not sure now how you'd tell it's a memory from pre windows 95 days :)) you can partition it not to use that area.

30-03-2013, 02:40 PM
May or may not help

Paul Ramon
31-03-2013, 05:43 AM
Try HDD Regenerator from here (http://www.dposoft.net/). Works great, I have repaired quite a few HDDs with bad sectors!

The Error Guy
31-03-2013, 12:47 PM
Apparently HDD Regen is pretty good (or so some of my searches say so) although I'm a little sceptical since it claims to fix "physical errors" - no way in hell THAT'S gonna happen!

Tried the trial on my internal laptop HDD - fixed the 4 bad sectors (had to run it 4x times, the trial only allows one bad sector recovered :D)

Looking at this 4890 from my external, I'd say that looks like physical damage to me, all concentrated in one space, although it could be due to a bad partitioning job since they are all around the 7-800GB mark. If the errors ARE physical, would WD take it back under warranty? I'm not hugely familiar with HDD's but I always assumed that bad sectors would be considered wear and tear? Or am I wrong?



31-03-2013, 04:04 PM
Did you try the manufacturers tools like I suggested? To my mind 3rd party software comes after trying the official software - which is also free.
For WD try http://support.wdc.com/product/download.asp?groupid=608&sid=3&lang=en

The Error Guy
31-03-2013, 09:25 PM
I thought I mentioned it earlier, perhaps I'm imagining things. I tried the WDC tools, it failed the quick test, something to do with not being able to complete the SMART analysis. I interpreted the message as "the drive failed the test because the software could not read the SMART attributes" perhaps it's meaning was relating to an actual error with the SMART status. All other software reads SMART and gives the drive a "pass" "ok" although HD tune gives "warning" which is very appropriate given the fact that it has damaged sectors. The warnings are for the Reallocated sector, event and the current pending sector count.

I'll give proper feedback on that tomorrow when I have the drive with me again.

Also figured out why the damned things show as "uninitialized" - WD have hardware encryption on their USB interfaces so the HDD is encrypted and can ONLY be used with a WD USB/SATA interface (and subsequently the USB interface won't work with a non WD drive) absolutely a pain in the ass for diagnostic/data recovery since I can't hook the drive up internally. It has to be via USB (unless I format it)

02-04-2013, 02:57 PM
You could try taking the logic board off and cleaning the contacts on it where the head connector ... connects. A dirty contact to the heads might cause problems like this, but it's unlikely to be the case.

You can't repair true bad sectors, only let the drive's firmware reallocate them itself.
They often indicate more problems to come. Sell it off, RMA it, throw it away, just don't bother trying to "fix" them, because it's not possible.

The Error Guy
03-04-2013, 09:13 AM
If they are physically bad then RMA or junk it is really the only way out, but I don't remember it getting any physical damage and the problem appears to be recent.

Being tight for cash I'm going to copy as much as I can onto a smaller 120GB and 600GB HDD, Zero fill it and see if that fixes anything. No change and it's off to WD to see if they'll be nice and replace it. If not I'll have to get a new drive.

Cheers for the advice etc. Hopefully it works out ok!