thanks Craig, so the main difference between a vitrualized machine on the new VT processors with anothe virtu machin on the old non-VT processors is performance ?
I use VirtualBox on my Pentium M 1.6GHZ which does not have virtualization instructions in the CPU. [I believe KVM requires the special instructions although I could be wrong]
The practical advantage is it is like having another machine (or two or three) running at the same time. So while working with Linux on my desktop, I can start up a virtual machine to do testing with. The virtual machine could be for testing, or perhaps running software that I can't run in Linux (say MS Windows software), or software that would normally require multiple machines, or software that would pose a risk to my machine.
The advantage of the technologies in the new processors is that it enables running virtualized machines faster and more efficiently. While this has obvious desktop benefits, it is targetted at data centres where they are running their server operating system ONLY on virtualized machines.
The practical advantages for a data centre is to be able to run multiple 'virtual' servers on a single physical server, and to be able to move the virtual server to another physical server with little or no downtime. For example, if your hardware fails, the virtual server could be automatically and transparently be moved to another physical server. If you require more processing power, you could shutdown unneeded virtual machines, and/or startup more instances of the needed server (for clustering).
Also, that virtual server can be tuned to the specific needs of that application, and applications can be kept separate from each other so they don't impact each others execution or security.
Many possibilities...
Last edited by Craig73; 05-01-2009 at 01:55 PM.
thanks Craig, so the main difference between a vitrualized machine on the new VT processors with anothe virtu machin on the old non-VT processors is performance ?
Well that is more the key benefit... but the technical differences and the implications I'm not as familiar with. I believe it gets into the differences between para-virtualization and full virtualization which someone else (or wikipedia) would be in a better position to clarify.
The performance difference can be huge.. With Qemu in full-software it's 10-11 times slower than your host machine. With Kqemu kernel module it's only 2-3 times slower, and with KVM it's about 10% slower.
At the time of the original tests VirtualBox only supported 1 vCPU and so tests such as the compile test were unfair (8vCPUs on kvm vs 1 on VirtualBox). Now that VirtualBox supports SMP in guests (up to 32 vCPUs) it would be interesting to see a re-run.
Any chance of that happening?