chs values

How to use TestDisk to recover lost partition
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ballisticbrian
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Joined: 21 Nov 2016, 10:42

chs values

#1 Post by ballisticbrian » 21 Nov 2016, 10:50

Hi guys, I recently had 3 drives all loose their data while putting computer into sleep mode (or coming out). I suspected the disk controller and bought a new PC.
However I can only access the disk via a USB port and they look unformatted to windows (I think).

I have had some extremely long scans of the main disk I need to recover with various errors. After the first scan, I managed to access the partition if found but their were just 2 directories and no files.

This time I put in the manufacturers (Seagate) CHS values and it is still scanning after 14 hours with large numbers of suspected partitions and mismatch errors.

I would like to know just how important are these CHS values as I've read somewhere they are arbitrary to how the computer accesses the disk? Or is this all about finding the correct values? Just to make it more difficult, the values I found at Seagate covered 4 hard drive models and 2 were 80gb and 2 were 160gb, which really doesn't make sense???

Any help appreciated. :)

I would just like to add that I had difficulty getting the BIOS to recognise these disks and went and bought a USB lead with a PATA connector. The error in Windows 7
was that the disk was "corrupt and unusable" and could not run chkdsk.
Last edited by ballisticbrian on 21 Nov 2016, 20:49, edited 1 time in total.

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cgrenier
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Re: chs values

#2 Post by cgrenier » 21 Nov 2016, 20:49

Old partitioning tools aligns partition to cylinder boundary. To recover lost partitions, a "correct" CHS geometry is needed.
But modern partitioning tools and modern OS (Windows Vista and later) creates partitions on 1-MB boundary, no need to bother about the CHS geometry in this case.

ballisticbrian
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Joined: 21 Nov 2016, 10:42

Re: chs values

#3 Post by ballisticbrian » 21 Nov 2016, 21:18

OK thank you for your help. Is it unusual that photorec_win can find lots of files but so far I haven't been able to recover the
partition using testdisk. All I've done so far is selected a couple of different options for the format type and had some various results with many errors or mismatches?

Also, I have already bought an identical donor drive in case it comes in useful.

Is it possible that drive electronics failure can cause the disk to look corrupt when it isn't? Is this just wishful thinking on my part?

Just as a reminder these disk, Windows 7 says "are corrupt and unusable" and chkdsk refuses to run. The other error I am getting is that he size of the disk is wrong - check jumpers and BIOS etc" however, there are no jumpers and the drive in in the USB port. Is this another case for switching the circuit board over possibly?

ballisticbrian
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Joined: 21 Nov 2016, 10:42

Re: chs values

#4 Post by ballisticbrian » 24 Nov 2016, 13:03

Is it possible to advise what to do next at this stage:
I have found a NTFS partition which is empty apart from two empty folders, Users and Program Files (x86).
The boot sectors appear ok in TestDisk although Windows still doesn't recognise the drive, I have to plug it into the USB.

The weird thing is undelete in Testdisk can find all the files that were deleted *prior* to the incident, mainly temporary internet files but nothing else.

It's almost like all my files have been wiped "zero'd off". Is there anything else I can do at this stage? Photorec can't find much more than the deleted files also.

Because this occurred to multiple disks on the same machine, my backups are gone. :(

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Re: chs values

#5 Post by cgrenier » 28 Nov 2016, 14:57

If you run PhotoRec, select the partition and choose [Whole] instead of [Free], do you recover your files ?

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