On Sun, 7 Sep 2008 08:22:28 -0400, "Tim Walsh" <tmwalsh@xxxxxx>
>"Bo Berglund" <boberglund@xxxxxx> wrote in message
>> In addition to my portability question yet unanswered I would like to
>> ask specifically about the handling of differencing disks:
>> When a diff didk is created it is about 30-40 kbytes in size. There
>> seems to be no other additional file concerning the differencing disk.
>> My question now is how the diff disk is handled if it is moved to
>> another location and this other location is not on the same drive as
>> before. Will a guest based on this diff disk be able to start at all?
>> I have looked in the vmc file of a guest created with the diff disk
>> and there is no mention in it that the VHD drive is a differencing
>> disk. So where is this information stored so it can be handled if the
>> guest is moved?
>> Or maybe such a guest is not movable at all?
>A diff disk is linked to an original disk, only the differences between the
>original are stored in the diff disk. The diff disk needs to be able to
>access the linked original disk in order to function. The use of a diff disk
>wouldn't be a good idea if your looking to move the VM from machine to
>machine on your flash drive, unless the linked file is also brought along on
>the flash drive.
>You might be better off using a dynamically growing disk, these also start
>out small but grow as needed up to your defined limit. You'll need a big
>flashdrive to use it.
The reason I am looking at diff disks is that I am creating a large
number of different test machines with XP-Pro on all of them. Using a
diff disk where the operating system files are the same makes for a
smaller disk footprint for the total exercise....
The system files need not be duplicated on all different guests, only
the different files I am testing will get to the individual diff disk.
I *am* keeping all files for my guests on the same removable drive,
basically I thought of this structure:
\VirtualPC\DiffPC <---- The original XP-SP2 parent disk here
\VirtualPC\DiffPC\XP1 <--- diff disk and vmc file for PC #1
\VirtualPC\DiffPC\XP2 <--- diff disk and vmc file for PC #2
\VirtualPC\DiffPC\XP3 <--- diff disk and vmc file for PC #3
\VirtualPC\DiffPC\XP4 <--- diff disk and vmc file for PC #4
I have looked in the diff disk file with a hex editor directly after
it is created (size 37 kb) and I found that there is stored both a
relative and an absolute path to the parent disk inside.
So I am wondering what will happen if the removable disk with all
these files is plugged into another PC where it will undoubtedly get a
different drive letter than the original?
Will the diff disk use the relative path or fail?
Bo Berglund (Sweden)