TestDisk shows different geometry (CHS) values?

How to use TestDisk to recover lost partition
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Posts: 1
Joined: 06 Mar 2013, 04:23

TestDisk shows different geometry (CHS) values?

#1 Post by Seaweed »


Running testdisk shows different CHS values (1 cylinder). After selecting disk and partition type, testdisk will show:

Disk /dev/sda - 320 GB / 298 GiB - CHS 38914 255 63

But at another time of the same testdisk session ( meaning I might have done some Analyse or Advanced on the disk, no Write, and then return to the main menu) or at different run of testdisk, the information is shown like this:

Disk /dev/sda - 320 GB / 298 GiB - CHS 38913 255 63

My questions:
- What does it mean having different values if cylinder like above?
- Is there something wrong with MBR?

Note: the disk is brand new and I was trying to use it as a clone for recovery partitions of another hard disk (different size). I copied MBR of the old disk and write it to the new one, hopefully to be able to restore the two recovery partitions of the old harddisk.

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Re: TestDisk shows different geometry (CHS) values?

#2 Post by Fiona »

Microsoft aligns partitions on megabyte boundary and Intel on Cylinder boundary.
Intel doesn't use the last cylinder of a disk.
In some cases partitions using the last cylinder of a disk.
In those cases, it was possible that you got a message that your partition is not recoverable anymore.
In previous TestDisk versions, it was possible to use the menu Option and the option "allow partital last cylinder".
In the meantime testdisk increases a disk one cylinder automatically so that users are allowed to recover partitions using the last cylinder.
It eases the the use of testdisk.