Sign in with
Sign up | Sign in
Your question

Bad sectors on HDD, now what?

Last response: in Storage
Share
August 19, 2010 5:05:36 PM

Hello to all people of this forum :) 

I have a 3.5" drive, Samsung HD300LD which used to be in my old desktop. That computer has mostly left this world but I am trying to salvage what I can. In case of the drive, I bought an external IDE-to-USB enclosure to use it as a storage for backups mostly.
Unfortunately, the drive has developed some bad sectors. 7 in total. I could not use it with the enclosure because of that and was also afraid I lost data from it. Today I had a chance to finally hook it up to a different desktop via IDE (curse these times where everybody only have notebooks...) and I successfully recovered all of the data and reformatted the drive.

Here is a screenshot from a disk utility I used from a linux liveCD with some info about the bad sectors:
  1. http://img806.imageshack.us/img806/2648/screenshot1j.png
I have a basic understanding of what happens when bad sectors appear: the hdd's firmware marks these sectors and substitutes them with some spare ones and all seems pretty transparent. From that disk utility it seems that 3 bad sectors are already substituted and 4 are not. I ran an error checking (and fixing) utility on both windows and linux but these numbers did not change.

My questions are:
1. Can I use this hard drive or is it going to fail hard soon?
2. Do bad sectors spread? Is 7 a lot?
3. Can I do anything else to the drive to make it usable? Should I be worried most bad sectors are not substituted?

Thank you for your time.

More about : bad sectors hdd

a c 415 G Storage
August 20, 2010 12:01:10 AM

If the numbers have been stable for a while then the drive is probably fine to use. You might want to do a full format and then re-check the numbers - if all goes well then I think the reallocated count will probably go to 7 and the pending count will go to zero. If the total count increases to something more than 7 then you've picked up some new bad sectors, and I'd take that as an indication that the drive is a little more questionable.

The "reallocated" sectors are sectors that at some point in the past gave errors when they were read but through retries and ECC codes the drive was able to recover the data from them and write it to alternate spare sectors. This is good - it means you didn't loose any data.

The "pending" sectors represent data that the drive hasn't been able to read correctly. Each time you try to read the data from those sectors the drive will try it's darnedest to recover the data. If it manages to do so then it will rewrite the data to spare sectors. If not, then the drive reports an error back to Windows and you'll see some red bullets in the system event log.

If you write new data to the "pending" sectors then at that time the drive will consider the old data to be expendable (you've asked to overwrite it, after all) and it will mark them as bad, reallocate the space to spare sectors, and write the new data to the spare sectors. This is why a full format should turn the "pending" sectors into "reallocated" ones - it writes new data to every sector on the drive.
August 20, 2010 9:33:49 AM

Hmm, I reformatted the drive on windows but the count is still the same.

What is a good windows tool for low-level format? The ones I find are for MSDOS...
Related resources
August 20, 2010 10:50:27 AM

Hmmm I cant edit my own messages here... strange.

Anyway I tried doing a zero-fill on linux but it failed and I dont really know why.
Here is how it went:
  1. root@ubuntu:/# dd if=/dev/zero of=/dev/sdb
  2. dd: writing to `/dev/sdb': Input/output error
  3. 6162633+0 records in
  4. 6162632+0 records out
  5. 3155267584 bytes (3.2 GB) copied, 315.073 s, 10.0 MB/s
August 20, 2010 1:45:11 PM

Windows 7 CHKDSK has this flag available:

/b NTFS only: Clears the list of bad clusters on the volume and rescans all allocated and free clusters for errors. /b includes the functionality of /r. Use this parameter after imaging a volume to a new hard disk drive.

So you could format your drive with NTFS and use chkdsk /b and see what happens.
a c 415 G Storage
August 20, 2010 3:33:25 PM

I suspect that "chkdsk/b" won't work because it affects the NTFS bad cluster list, which is different from the bad sector mapping tables inside the drive itself.

If a full format doesn't clear the "Pending" count then I don't think I'd worry about it too much. The most important thing is that you're not seeing any new bad sectors.
!