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Re: [Xen-users] virtualbox vs. xen - ease of domU installation

On May 15, 2008 11:54 am Miles Fidelman wrote:
> I've just started playing with Virtualbox - and boy do they make
> installing virtual machines easy.  Download an .iso of a netinstall CD,
> point Virtualbox at it, and you have a window that behaves just like a
> normal install.  Worked like a charm with both Debian Sarge and Etch
> images - doesn't seem to require any special bits in the guest O/Ss.

VirtualBox is based on a modified QEmu.  It emulates a complete computer, 
right down to the BIOS, including a bunch of standard hardware 
components.  As such, you don't need to modify OSes to run then on the VB 
VM.  VirtualBox doesn't (AFAIK) use the hardware virtualisation support 
in Intel/AMD CPUs, and does a bunch of software tricks to run the VMs.  
Not sure if it uses the KQemu accelerator module or not, or anything 
similar.  As such, running VMs in VirtualBox will be slower than other 
solutions (that uses accelerator modules, hardware virtualisation 
support, etc).

The closest comparable product for VirtualBox would probably be VMWare 
Server or VMWare Workstation (in how they create a total virtual 
computer, with a pretty management GUI).  They work roughly the same 
(doing everything in software).

Xen can also run unmodified guests OSes when installed on systems with 
motherboards/CPUs that support Intel's VMX or AMD's SVM hardware 
virtualisation extensions.  Xen uses a modified QEmu to create the 
hardware VM (emulating a bunch of standard hardware), and as such, you 
can run unmodified guest OSes.

KVM can also run unmodified guest OSes, when installed on systems that 
support VMX/SVM.  KVM uses a modified QEmu to provide standard hardware, 
and can run unmodified guests.

(As all but VMWare use a modified QEmu base, it's fairly easy to move VMs 
between products.  I've run Xen HVM images under KVM, and KVM images 
under QEmu.)

And, of course, there's also QEmu.  :)

Freddie Cash

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