[vbox-dev] Snapshots with VirtualBox

Frank Mehnert frank.mehnert at oracle.com
Mon Feb 9 07:58:54 GMT 2015


On Sunday 08 February 2015 20:49:33 Thouraya TH wrote:
> Please, i ask if there is a paper which present statistics about the size
> of snapshots (dumping) with virtualBox ?

such statistics do not exist. The space occupied by a VirtualBox snapshot
depends on the guest operating system.

If the VM was powered on while doing the snapshot, a saved state is created
which reflects the VM state at this time. It's size is mainly defined by
the amount of RAM which is assigned to the guest OS. The saved state is
compressed. If the VM was powered off, no saved state is created.

The other part of the space occupied by a snapshot is defined by the
differential images which are created for all attached virtual hard disks.
Every sector written after the snapshot is created goes to the differential
image. The more data the guest writes the more space is occupied by the
differential image. In the worst case, every differential image occupies as
much space as the corresponding base image.

Dr.-Ing. Frank Mehnert | Software Development Director, VirtualBox
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