Bad sectors on hard disk

How to repair it please? Any free software available to automatically repair bad sectors of the disk?
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  1. You cannot repair bad sectors. The term "Bad Sectors" usually is used by Windows as it reports results of several utilities like SCNDSK. What it really means is that, during its testing, it found some Sectors could not be read reliably. So, it tried to copy the data there to another good sector and adjust the file allocation records to take this into account. Then it placed an entry in its own Bad Sector table that it keeps on the drive. From now on Windows will NEVER use that sector, or any others in that table. But you must be a little careful, because the copying of data from Bad to good sector MAY have copied BAD data because the source sector had a flaw. The big trouble is that these Windows utilities never tell you which files had the problem, so you can't know where the potentially corrupted file(s) is (are).

    There are two ways to get rid of Bad Sectors, and neither of them is a repair. Each simply avoids ever using them again. And MOST IMPORTANT - BOTH of these completely destroys the data on the drive!!

    The first is done using Windows itself - you Format the drive, doing a Full Format. As it does that, Windows tests all the sectors and replaces the old Bad Sector table with a new one. This does not eliminate those Bad Sectors - in fact, the ones that really are bad will be re-detected and put into the new table.

    The second is to force the HDD itself to do the job and "hide" the results. This uses a normal background function of the HDD's own on-board controller. You need a utility that will "Zero Fill" the drive. This writes just zeroes to EVERY sector of the drive. In doing so it also tests every sector. If any are found to be questionable - even weak is found this way, not only really bad sectors - it is marked in the HDD's own hidden records and replaced with a known-good sector from a stock of spares. Actually, this process goes on all the time during normal operation, but sometimes it misses a few weak sectors. Anyway, when this is finished you have a completely blank drive like a new one, and it MUST be Initialized - that is, Create a Partition and Format that - so that Windows can use it. But at this point the drive does not let Windows see ANY bad sectors - they have all been replaced with good ones - so Windows will report no Bad Sectors.

    To repeat, neither of these processes repairs Bad Sectors - there is no repair process. They each just replace bad sectors with good ones. And BOTH completely DESTROY all your old data on the drive.
  2. also before you you format your hard drive run hdtunes and read your hard drive smart report. drives do over time get one or two bad spots. the issue is if the hard drive heads heads are hitting the platter or if the media is going bad. the smart read will tell you how many sectors have gone bad and if there close to the drive vendor max count. if it is close you may want to see if your drive is under warranty and replace it. hard drive will start clicking or humming if the heads or bearings start to go.
  3. Bad sectors:

    1. COPY all data to another drive
    2. Run a full diagnostic using the software from your hard drives manufacturer (should be a DESTRUCTIVE diagnostic which is why you copied your data).
    3. Do a FULL FORMAT of the drive.

    - if any data is already corrupted it can't be repaired
    - the FULL FORMAT not only formats the drive, but also builds a BAD SECTOR table by writing and reading to every location; those areas that aren't reliable are blocked off. You should ALWAYS perform this prior to use the first time, especially before Installing Windows.
    - both the diagnostic and format will take hours (perhaps 5 hours per TB)
  4. If you have bad sectors in your hard disk, running a program such as Microsoft CHKDSK or ScanDisk and performing excessive attempts to read the disk can make matters worse. Your best chance of successful recovery of your data is to take your drive to a data recovery specialist and allow them to examine the disk.

    Read my data recovery blog for more information about sectors and the causes of bad sectors.

    John Reid, Cheadle Data Recovery, Manchester, UK.
  5. Sorry if this is resurrecting a old thread but there was no good answer and a very wrong one from paperdoc.

    Had regenerate

    That software REPAIRS bad sectors without data loss.
  6. Interesting product, HDD Regenerator, in your link. I see it uses a unique technique to read remnants of old data. The software claims that about 60% of "Bad Sectors" can be re-read properly, thus restoring the original data. That seems reasonable to me. A lot of "Bad Sectors" in fact merely contain one or more corrupted bits that often are really just bits recorded with weak magnetic signals; hence I can accept that such flaws can be read correctly with advanced techniques.

    Of course, sometimes the corruption is so severe that even these advanced techniques can't succeed. Additionally, there are other causes of failure (such as a "head crash" that physically damages the magnetic film) that would defy data recovery. So 60% success seems a reasonable claim. And that's a LOT better than 0%!

    Modern HDD's have their own built-in mechanisms to deal with errors. These processes are not apparent to the Operating System since they run internally in the HDD on its own processor system. In outline, every time a Sector is read, the HDD's system makes an assessment of the quality of the signals. All OK, then just continue on. If there's an error in the data (checksum techniques or whatever used) the system tries to recover good data from the Sector. I don't know exactly how - one method is re-reading several times and getting an average, but I'm sure there are others. If this succeeds in retrieving all good data, it is written to a new known-good Sector from the unit's spares list and the "bad" sector thus identified is marked in the HDD's own files never to be used. Even if the data are OK but the system judges the signal strength to be too weak, it will take those measures as a preventive step. Then the data are sent out to the OS that requested them, with NO flag that any of this was necessary. But the HDD system also keeps track of how often this repair was needed as part of its SMART system. Among other tasks, that system eventually will exceed its limit and send out a SMART warning of high error count. The user's best choice when that happens is to replace the HDD while it is still able to deliver all of its data un-corrupted.

    If the HDD's internal operations cannot recover good data from the faulty Sector, it still replaces it, but in this case the data in the replacement Sector is known to be corrupted. So it DOES tell the OS that requested the data that there was a Read Error and the data are "Bad". THIS is when Windows (or other OS) recognizes it has found a "Bad Sector" and does its own thing about never using that spot again. But Windows itself has NO tools for trying to recover good data from a "Bad Sector", other than asking the HDD to re-try the Read operation a few times and hoping it succeeds.

    So the HDD unit itself has ways to detect and "fix" a Bad Sector. The "fix" does not repair that Sector. It works hard to retrieve the original data un-corrupted from there and then writes it to a new reliable Sector. This can take care of many errors and save data from weak areas of the HDD even though you and your OS don't even see it happening. But by the time Windows reports a "Bad Sector" containing corrupted data, these processes already have been applied and failed. Recovering data from such a situation requires different techniques, perhaps like those of the HDD Regenerator software.
  7. Pravin2013 said:
    How to repair it please? Any free software available to automatically repair bad sectors of the disk?
  8. RE-read my post of Feb 7/13. That outlines two free "repair" tools. But the important point for BOTH of these is that they both destroy ALL the data on your HDD!! Also, neither of them can REPAIR anything. They both simply find all the Bad Sectors, mark them for never using again, and replace them with Good Sectors left over from the original manufacturing of the HDD unit.

    So, BEFORE you try to use either of those tools, you MUST make a complete copy of your HDD to preserve your data.

    The product discussed above on Aug 18/13, HDD Regenerator, is a different tool which MAY be able to recover your data from weak Sectors. It's not guaranteed to succeed every time, but it is much better than having no tool to use! However, I'm sure it is not free. Again, it does not REPAIR a Bad Sector. It works hard to recover your data from the Bad Sector and write it to a replacement Good Sector before hiding the Bad on so it will not be re-used.
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