The two companies are promising support for one another's virtualization platforms: Novell's is the open-source Xen hypervisor that ships with its Suse Linux Enterprise Server (SLES) 10. Microsoft's is in its upcoming Microsoft Virtual Server 2005 R2 Service Pack 1 and in the future edition of Windows Server that is still code-named "Longhorn."
Under the agreement the two will allow SLES to run as a guest in Microsoft Virtual Server, and as a "paravirtualized" guest on top of Longhorn.
Paravirtualized guests split the difference between the privileges of a native operating system and a completely virtualized guest operating system. Rather than passing all requests through the control of the hypervisor, a paravirtualized guest has access to the application binary interface (ABI), the set of specifications the operating system uses to communicate with its component parts. Operating systems with totally compatible ABIs would allow one application to run on both unmodified.
Longhorn will also be able to run paravirtualized on the Xen hypervisor.
In order to let Longhorn run on Xen, however, Microsoft has to develop a special version that runs with less potential conflict, and supports more low-level code than it as an unmodified guest.
Unmodified guests often require virtualization-enhanced chips such as the AMD-v or Intel-VT.
The original version of this story appeared on TechTarget sister site SearchServerVirtualization.com.