Hard Disk Details(7)

Slide 3791: The cause of the click is from four possible areas, all resulting in the SA not being able to be read.

1.    System Area of the drive cannot be read because the platter is scratched.

2.    The head itself has a problem and cannot read the SA area.

3.    Preamp on Actuator to the Head has gone bad and is not passing the correct signal to the electronics

4.   The firmware on the board is damaged and does not initialize. This is sometimes caused by static electricity walking across the carpet to install the drives, or there is a short on the board, and additionally I see where someone has allowed the board on the bottom of the drive to touch metal cause it to burn.

All will result in the same problem and will sound like the Click of Death. Recovery Software will not help you correct any of these until after you have repaired the drive and it is running again.

Correcting Problems
Now we move on to some of the things you can do about it on your own.  The click of death is a very difficult problem to solve and in some cases will not be able to be solved especially without some very high end and expensive equipment. But I will tell you what I have been able to fix without that equipment.

Slide 4009: Swapping the PCB (printed circuit board) Live to get around a SA area that cannot be read.

I have done this process several times successfully. It is not perfect but it is a possible chance you will have to recover your data. The first step is to get a hard drive as close to identical as the bad drive you have that is a working drive. At the bottom of this paper you will find help about matching hard drives and serial numbers. If the System Area is badly damaged or corrupt and for some reason the drive will not read the System Area you can attempt to do a live swap. What this means is that you can hook up the good drive, then you use software or windows and tell the drive to go to sleep.  This will cause the drive to spin down but will still be live and powered up and mounted.  Once the drive goes to sleep and the drive stops spinning you can unscrew the board, carefully so as not to let the screws roll around on the board, and disconnect the board and connect it to the bad drive. I suggest that once you do this, you go after the files you need very quickly. It’s possibly you will be able to make an image of the drive.  Keep in mind, that whatever bad blocks that the drive had assigned to the other drive will be bad here as well.  You could try to use some software to clear bad blocks before attempting this, however I don’t suggest it in most cases. That is because it is one more possible item that might cause failure. I would prefer to use the drive that was working and lose a few blocks. After you get what you can then you can attempt to make changes and go back for more data. This is a concept that works about 25% of the time.

Slide 4199: Imaging in Reverse

In dealing with damaged hard drives, I have run into many problems with cache memory on the drive. The problems will often show up as timeouts or ECC failures as well. For example, I try to read from a drive with16 megs of ram for cache and receive errors but the drive is otherwise appears ok. If there is an error 16 megs away from the sector I am reading my drive will die. As of now there is no way to turn off this cache.  However, if you can image your drive backwards there is no cache. Memory on a drive only caches data forward. There are only three ways I know of to image a drive backwards. The first is free, and it is to use dd_rescue. dd_rescue has a special setting for imaging a drive backwards. There is also a special script for dd_rhelp to control dd_rescue for the purpose of data recovery. You can use this on Linux and it works on drives regardless of the operating system on the drive you are recovering from. Typically you will start at the MaxLBA number and work backwards down to 0 LBA. It works quite well and will work on a surprising number of drives that cannot be read any other way. Your other two choices are Media Tools Pro from RecoverSoft (http://www.recoversoft.com/) for Windows, which is about $400, or a piece of hardware which is extremely efficient at doing this type of recovery called Deepspar Disk Imager (http://www.deepspar.com/products-ds-disk-imager.html), which will cost between $3000 and $4000 depending on configuration. But you should contact each of these vendors for pricing, or use the free option!

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