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Bad Sectors

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September 18, 2008 5:31:16 PM

Hi guys, hope you can enlighten me on the following issues about bad sectors detected on HDD:

1. Can 'bad sectors' be repaired?
Apparently by running Hitachi DFT's "Erase Disk", the bad sectors are gone and none are detected thereafter.

2. Can all hdds with bad sectors be repaired by the above method?
I always have the impression that a drive with bad sectors is beyond repair and have to send in for replacement.

3. Where do the bad sectors go? Marked as "not usable"? If that is the case, how can i be sure? (Using chkdsk, it shows no bad sectors)

4. Will it actually affect performance?

5. Is there a non-destructive way to repair bad sectors?

6. What causes bad sector? Hardware or software/OS?

7. Are there any concerns that i reuse the hdd again? Will it fail soon?

8. Finally, should i send in for replacement even though it does not show any bad sectors?

(I am referring to a Hitachi 250GB 2.5" hdd that I bought about 4 months ago.)

Thanks in advance.

More about : bad sectors

September 18, 2008 6:04:58 PM

singtech08 said:
Hi guys, hope you can enlighten me on the following issues about bad sectors detected on HDD:

1. Can 'bad sectors' be repaired? - Yes, but they have to be REALLY tested before returned for use. I don't know diddly about Hitachi DFT's "Erase Disk", but I can recommend Spinrite by Gibson software big time. http://www.grc.com/sr/spinrite.htm

2. Can all hdds with bad sectors be repaired by the above method? - Yes - really same as question #1

3. Where do the bad sectors go? Marked as "not usable"? If that is the case, how can i be sure? (Using chkdsk, it shows no bad sectors) - Correct, marked as not usable - checkdsk has no idea they're there anymore

4. Will it actually affect performance? - NO, well not really. head will have to get past bad to reach good.

5. Is there a non-destructive way to repair bad sectors? - YES

6. What causes bad sector? Hardware or software/OS? - YES (both). faulty application of magenetic media in factory can cause sector to fail. magenetic field failing over time can cause sector to fail (ever try to use a 5 year old floppy that hadn't been used since day one? it's going to show as unformatted). software/os failure to ensure that data was properly written to drive can make a sector show'bad' when its really 'corrupted'.
7. Are there any concerns that i reuse the hdd again? Will it fail soon? Maybe. if its a software issue you'll be ok. if hardware? - make a clock out of the disc platters.

8. Finally, should i send in for replacement even though it does not show any bad sectors? if it doesn't show bad sectors, how are you going to get them to replace it?

(I am referring to a Hitachi 250GB 2.5" hdd that I bought about 4 months ago.)

Thanks in advance.



Here's the deal. Get a copy of Spinrite from http://www.grc.com/sr/spinrite.htm. Boot to it, tell it to test your system as intensively as it can - then come back later and see what the results are.

Spinrite will do a non-destructive low level format of the disk and recover the sectors that are good but marked bad, locking out the ones that are bad, etc.... It's non-desctructive cause it makes copies of a sector before the test or something...and it REALLY tests the cr@p out of each sector. Last time I looked it writes/reads each bit 65536 times before it marks a sector as bad.

I don't know the guy, I don't get any money out of it - but I've been impressed by the product for a long time now, and make it part of the required purchases of any tech shop they have me go save/create. I've used it since v4.0, and it's simply the best disk tester I've ever found or heard of.
a c 359 G Storage
September 18, 2008 6:22:52 PM

You should understand that the HDD unit itself is hiding things from you. The 250 GB HDD has more space than that on it. When manufactured it sets up its opn internal tables in its on-board controller that allocates 250 GB worth of good sectors to be used. Then it sets aside, hidden from you, more good sectors as a reserve. As the disk is used it constantly checks its own operations in the background. When it decides a sector is becoming unreliable it will copy the info to a spare good sector, mark that as a good sector in use, and then mark the bad sector as such so it won't be used again. Much later you may get around to running a disk-checking utility from the disk maker and one of its jobs is to update all this kind of info in the HDD's own internal memory. Then it hides all that. Although it has simply marked the bad sectors as no longer available and replaced them with good ones from the spare pool, to you it looks like it magically fixed the bad sectors because they are all gone!

This process will continue throughout the drive's life. One of the functions of the S.M.A.R.T. monitoring systems on HDD's is to check that this process has worked OK, and that there still are spare good sectors to use when needed. When the pool of good spares gets down to a lower limit, the S.M.A.R.T. monitoring system puts out a warning of impending drive failure so that you have time to replace it before all the good spares get used and you really do lose some data.

So, no, you can't fix a bad sector. Some low-level utilities may do a better job of testing sectors and deciding whether they really are too bad to use, or maybe they are OK and can be moved back into the "good spare" category. That's about as close as it comes.
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September 19, 2008 2:09:13 PM

Not all bad sector on hard drives are hard, there are times when during a power surge your drive fluxes the platter under the heads corrupting the low level format, thus running spinrite or hdd regenerator will fix these.

What i find strange is the lack of hard drive repair software out there the only one that works is spinrite and hdd regenerator other than the there is nothing else.
September 20, 2008 8:11:13 AM


thank you guys.

your answers are prompt and comprehensive.

i got all the answers that i need.

thanks. :wahoo: 
!