On Thu, May 19, 2011 at 11:45 PM, Adam Moffett <[email protected]> wrote: > I used virtualbox on my workstation for several months before I actually > looked at the manual today.....so my compliments to whoever designed the > user interface. You definitely made it intuitive. > > 1) I found in the manual that a snapshot is storing the difference between > the contents of the guest's disk now and its contents at the time of the > snapshot. That being the case, does that mean that snapshots gets updated > every time the guest's disk changes? Doesn't that mean every disk write on > the VM = two writes on the host? Or if I had 3 snapshots of the same VM, > wouldn't that mean that each write on the guest = 4 writes on the host....or > does Virtual Box just store the difference from one snapshot to another in > order to avoid duplicating the same data? In either case, it would seem > wise to store snapshots on different physical media than the VM disk images > to avoid the performance hit.
VirtualBox has several layer. Once you create snapshot, previous layer becomes read-only. 1.Base image (normal VDI) (read-write) -- just like physical hard disk. 2. You create first snapshot. Base image becomes read-only. Base image (normal VDI) (read-only) +-- Snapshot 1 (read-write) 3. You create another snapshot -- all previous layers become read-only. Base image (normal VDI) (read-only) +-- Snapshot 1 (read-only) +---- Snapshot 2 (read-write) Write is performed only against latest layer, and only once. > 2) From the section in the manual regarding 3D acceleration: "When an > application in the guest then requests hardware acceleration through the > OpenGL or Direct3D programming interfaces, these are sent to the host > through a special communication tunnel implemented by VirtualBox, and then > the host performs the requested 3D operation via the host's programming > interfaces." I think this implies that in the case of a Windows guest on a > Linux host Direct3D will never work since the Linux host can't do that. Is > that the case? If VirtualBox does take Direct3D commands from the guest and > convert them to OpenGL for the Linux host then I will be suitably impressed. > Your assumption is incorrect. VirtualBox uses only *OpenGL* on it's host side. OpenGL commands are transferred to host's OpenGL drivers, using Chromium layer. For Windows guests, Direct3D calls are converted to OpenGL instructions by GuestAdditions (using WineD3D). This happens inside the Guest itself, so host gets OpenGL commands. -- -Alexey Eromenko "Technologov" ------------------------------------------------------------------------------ What Every C/C++ and Fortran developer Should Know! Read this article and learn how Intel has extended the reach of its next-generation tools to help Windows* and Linux* C/C++ and Fortran developers boost performance applications - including clusters. http://p.sf.net/sfu/intel-dev2devmay _______________________________________________ VBox-users-community mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/vbox-users-community
