Datasheet

SYSTEM OVERVIEW
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the market leader. Both VMware and Virtual PC are Type 2 virtual machines. Figure 1.8 shows
a Type 2 hypervisor.
Figure 1.8
Type 2 operating
system
Virtual machines are often used to test applications and system configurations, to set up systems
for performance testing (such as web clients used for loading), and to sandbox applications that
might be unstable (such as beta software) or unsafe (testing viruses and malware). Sandboxing
isolates applications from other programs on your system, and is used both for security and com-
patibility reasons.
Hyper-V adds virtualization capabilities directly into Windows Server 2008 (Figure 1.9), and
creates a thin-layer Type 1 hypervisor that will co-exist with their type 2 Virtual Server product.
You can run both or either of these two products individually, or migrate from the Virtual PC
to the more powerful hypervisor product. The advantages of such a system is that it will allow
finer control over hardware than a Type 2 system, easier dynamic allocations, and subsocket
partitioning.
When Windows Server 2008 ships, Windows Server virtualization will allow systems to run up
to 16 cores or logical processors at a time. The original plan was to allow for 64 processor instances.
Other features that were scaled back to allow Windows Server 2008 to ship at the beginning of 2008
were some of the hot-add capabilities for both storage and memory. Hot swap, hot add, and Live
Migration, as well as 64-processor limits, are features that competing products already have.
This version finally adds support for 64-bit programs running in 64-bit guest sessions, some-
thing that the earlier version couldn’t do. Eventually Microsoft virtualization will permit users to
migrate live systems entirely from one virtual system to another, and support the hot swap and hot
additions of processors, memory, networking interfaces, and storage—but these features did not
ship with the first release of Windows Server 2008 and were delayed until later. A Type 1 hyper-
visor should enable features like the hot edition of a network card or processor without reboot. The
current plans are to have Windows running up to eight processors, and from 4GB to 32GB per each
virtual machine.
Virtualization is an important feature, and is now part of competitive server platforms such
as SUSE and Red Hat Linux, both of which have incorporated VMware into their systems. These
systems use the Xen open source virtual machine, which is currently at version 3.0. This version
will run Windows as a guest, and XenSource is expected to release a compatibility layer for the
Windows Server 2008 hypervisor. Systems that run Xen guests can use this compatibility layer to
move their sessions to Windows Server 2008. Xen is a Type 1 hypervisor; it runs in Ring 0 while its
guest OSs run in Ring 1.
Application
Operating
System
Application
Operating
System
Application
Operating
System
Hypervisor
SMP Server
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