Differencing virtual disks

P.O.W. · Post by **P.O.W.** » 24. Jun 2007, 01:11

I read about support for "immutable images" here: http://forums.virtualbox.org/viewtopic. ... =immutable,
however this is a very tricky way.

Can be more friendly to mark as immutable a vdi when you create a snapshot (and allow direct copy of vdi for use in a new virtual machine without use of clonevdi).

In this way could be great to create snapshots as in a tree, instead than a chain, where the root is the immutable vdi and the other levels are differencing.

Stormwind · Post by **Stormwind** » 8. Sep 2007, 05:18

I just wanted to concur that this feature is very desirable.

I believe VMWare calls this feature base virtual disks, and Virtual PC calls it differencing disks.

Why I'd like the feature: Notebook computers have limited hard drive space. I'd like to have one base image with a Windows XP install, and multiple child images for several different applications. With a base virtual disk having the OS install, the child images would be much smaller differences since they would all share the common data (the OS install) from the base image.

alexei · Post by **alexei** » 13. Oct 2007, 11:07

I'd like to have differencing disks that reflect difference to a disks used by the Host OS that would allow to "run OS under itself". What I mean is to use same OS as Host and Guest, though changes made by Guest are not reflected on physical drive. Of course, changes made by the Host should be also "virtualized" to become invisible to Guest.
Alternatively, similar functionality can be implemented as a virtual drive that has most of files "mapped" to the files on a Host's shared drive in a way invisible to the Guest OS. Such approach would allow Guest to use Hosts's files even if they are physically relocated.

Technologov · Post by **Technologov** » 14. Oct 2007, 07:17

I also need differencing disks...