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had the technology bought and paid for in their server operating system. No longer would they have
to research, select, and download a product before installing it — more often than not on a
dedicated physical server.
Hyper-V is more than just a software feature which gets installed within Windows though, it's
a component which sits deep within the operating system itself, and in some areas is closer to the
physical hardware than Windows itself is once Hyper-V is enabled. It's this low-level code that
allows Hyper-V to schedule all of the different CPU requests its virtual servers make and allocate
them CPU time so they can run.
Not all of the reaction to Hyper-V's initial release was good for Microsoft though. The i rst version
suffered from the usual inadequacies of v1.0 software we've become used to. In fact, it wouldn't
be unfair to say that the version that shipped with Windows Server 2008 was unsuitable for most
production workloads. However, progress was made in making people aware that Microsoft was
entering the server virtualization market.
Signii cant improvements were made to Hyper-V in Windows Server 2008 R2 and again with
Service Pack 1. Live migration, dynamic storage, Dynamic Memory, and enhanced processor
feature support made deploying Hyper-V in a busy production environment a reality. It is likely
that many of the people who have chosen to adopt Hyper-V have done so because of Microsoft's
dominance and reputation with other applications, along with the pricing model.
In the same way that VMware offers a hypervisor product and an enterprise management platform,
vSphere, so does Microsoft. System Center Virtual Machine Manager is a suite of management
tools designed to manage large Hyper-V environments, as well as deploy, orchestrate, and monitor
private clouds. Known sometimes as just VMM, it's not as widely adopted as vSphere, but I suspect
that will change as Hyper-V is adopted by more and more enterprise-scale customers. System Centre
Virtual Machine Manager 2012 has been released with many private cloud management capabilities
built into it and will be core to Microsoft's server products strategy over the next few years.
Windows Server 2012 enhances Hyper-V's capabilities with a compelling update of the feature. Its
virtual servers will support up to 32 virtual CPUs and 1TB of memory each, while support for
replication of virtual servers will offer new high availability capabilities.
Xen
Of the three server virtualization products covered in this section, XEN is undoubtedly the rarest
and least widely adopted. Xen was the output of a research project by the University of Cambridge
in the early 2000s, and its legacy was an open-source hypervisor. Although the open-source version
still exists, a number of commercial versions are also available. Citrix Systems now owns and sells a
commercial version of it known as XenServer, while the technology has also been adopted by vendors
such as Sun and Oracle. Of more interest, however, is its adoption by a number of cloud service
providers such as Amazon and Rackspace, demonstrating that cloud technology does not differ
fundamentally from on-premise technology.
Hardware Support for Virtualization
While we can very easily see and interact with the virtualization software we install on our servers,
what we can't see is that the CPUs inside our servers now have components built into them to
assist with virtualization. In the same way that CPUs had specii c logic and components added to
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