Re: [Xen-users] Is Xen really a Type 1 Hypervisor?

[Peter Viskup <skupko.sk@xxxxxxxxx>]

On 11/20/2012 10:03 PM, quadibloc wrote:
> While Xen is indeed actually a Type 1 hypervisor, confusion is
> understandable.
>
> With VMware ESXi, another Type 1 hypervisor, you install ESXi on a machine
> using an ESXi install disk. And then ESXi runs on that machine, hosting
> whatever guest operating systems you install on it. You manage the
> hypervisor over the network from another machine, which may be running
> Windows, running the vSphere Client.
>
> VMware used to make a Type 2 hypervisor called VMware GSX Server, which ran
> on top of a server operating system, and which could therefore be managed
> from the keyboard and screen of the server itself.
>
> When you install Xen, though, you use a Linux install disk. After you have
> installed Linux, you add a Xen package which both puts Xen administration
> tools in the copy of Linux you have installed, and installs Xen itself as
> another operating system. Then you use GRUB to switch things around so that
> Xen boots up, but it still subsequently starts that copy of Linux as a
> special guest operating system with the power to administer Xen.
>
> So it's a Type 1 hypervisor that does a good job of appearing like a Type 2
> hypervisor if you don't pay attention to what's going on technically behind
> the scenes. You install Linux, then you boot into the Linux that you
> installed to control the hypervisor - just as you would have if it were Type
> 2.
>
> --
> View this message in context: 
> http://xen.1045712.n5.nabble.com/Is-Xen-really-a-Type-1-Hypervisor-tp5643400p5712507.html
> Sent from the Xen - User mailing list archive at Nabble.com.
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxx
> http://lists.xen.org/xen-users
Hi quadibloc,
Xen definitely is type1 hypervisor. You have to differentiate between 
Xen hypervisor and dom0 management domain. In VMware ESX you have both 
hypervisor and management stack in one 'package', but in Xen it's not. 
Xen has separate small-size hypervisor running directly on top of HW and 
dom0 is started just on top of it. dom0 is communicating via special 
communication channels with Xen hypervisor and providing only management 
stack. Therefore the dom0 kernel needs to be patched to support this 
communication channels and it could be GNU/Linux or NetBSD or any other 
system you would like to patch to support Xen management.
Xen's advantage of ESX is that it doesn't need to 'support' the HW it is 
running on. The HW needs to be supported only by dom0.
For better understanding read this: 
http://wiki.xen.org/wiki/Xen_Overview and continue with 
http://wiki.xen.org/wiki/Xen_Beginners_Guide .
Best regards,
--
Peter Viskup

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
http://lists.xen.org/xen-users