RE: [Xen-users] differences between Para-Virtualization andFull-Virtualization?

Artur Linhart - Linux communication
Sat, 21 Jul 2007 20:12:47 -0000

Hello,

	I think it is true what Nico writes, but I would say - from the
philosophical point of view of me the main difference between full
virtualization and paratirtualization is in the fact, the fully virtualized
OS "does not know" it runs on some emulation of the computer and there
can
be some other OS instances with which the resources can be shared, but
paravirtualized can. It means, in paravirtauliyation can be also changed the
disks, CPUs, memory etc. During the run of the system and the guest OS can
handle this changes correctly.
	The consequence is then, the paravirtualized system can generally
know more about the system where it runs because it can cooperate with the
hypervisor.
	I do not think it is an exact information there must be some kernel
etc. with some special properties - there exist also paravirtualization
drivers for windows to cooperate with the hyparvisor - and windows have no
kernel in the linux meaning...

	With best regards

		Archie

-----Original Message-----
From: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of thewird
Sent: Friday, July 20, 2007 10:55 AM
To: Nico Kadel-Garcia
Cc: xen-users@lists.xensource.com
Subject: Re: [Xen-users] differences between Para-Virtualization
andFull-Virtualization?

> > Hi,
> >
> > Could someone explain me the following questions:
> >
> > Where are differences between Para-Virtualization and
> Full-Virtualization in the aspects of memory management, CPU and
> Device I/O, Network?
> >
> > How is the performance difference between them?
> >
> > Thanks
> > Songtao
> There are dozens of good documents on this. Boiled down to a few
> lines,
> full virtualization emulates the entire hardware platform of a guest
> computer. That can be effective for running an otherwise incompatible
>
> operating sytem, like Windows on a Linux server.
>
> Para-virtualization uses a customized kernel, compatible with the
> host''s
> kernel and "hypervisor", that speaks compatibly and much more
> directly
> to your host''s hardware. It''s much lighter weight, allows
memory to
> be
> re-allocated among guest domains so a server can run far more guest
> domains,, and provides a really noticeable to any guest operation
> that
> has to talk to the disk. But it requires a compatible kernel on the
> guest OS, compatible with the Xen version of the host OS.

How would one go about compiling his own compatible kernel on the guest
OS? What needs to be done to the kernel.

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