Where are differencing images stored, physically?

[matteosistisette]

Hi,

I've read the parts of the manual regarding snapshots and differencing images, and I am still not sure about one thing: where are differencing images stored?

Suppose I have a simple VM with a VDI for its main hard disk. I know where the file storing the VDI is (I created it in a folder which is not the default one). And it's in normal mode.
Now I take a snapshot. I notice that a file has been created in ~/VirtualBox VMs/my_vm/snapshots
Somehow this file "is" the snapshot.
I understand that now my VDI stops growing, becomes kind of "read only" and all changes will be stored in a differencing image. Is the differencing image contained within the snapshot file? Or will a separate file be created for the differencing image? If so where? I haven't seen any other file be created apart from the snapshot file...

thanks
m.

[matteosistisette]

Ok, I've realised the file created in the Snapshots folder is actually the differencing image.

So now my question is kind of vice versa. A snapshot is supposed to also contain a copy of the VM settings (i.e. the virtual hardware). Where is _this_ information stored? Is it stored within the vdi file as well, together with disk data??

[mpack]

The snapshots folder holds difference images. Referring to these files as snapshots is convenient shorthand but somewhat inaccurate. In reality a snapshot is a combination of disk state and control information: the .vbox file holds all the control info, including for the current state and for all snapshots.