Datasheet

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CHAPTER 1 INTRODUCING VMWARE VSPHERE 5

VMware vSphere Compared to Hyper-V and XenServer

It’s not really possible to compare some virtualization solutions to other virtualization solutions

because they are fundamentally different in approach and purpose. Such is the case with VMware

ESXi and some of the other virtualization solutions on the market.

To make accurate comparisons between vSphere and other virtualization solutions, you must

include only type 1 (“bare-metal”) virtualization solutions. This would include ESXi, of course,

and Microsoft Hyper-V and Citrix XenServer. It would not include products such as VMware Server

or Microsoft Virtual Server, both of which are type 2 (“hosted”) virtualization products. Even within

the type 1 hypervisors, there are architectural differences that make direct comparisons difﬁ cult.

For example, both Microsoft Hyper-V and Citrix XenServer route all the VM I/O through the “parent

partition” or “dom0.” This typically provides greater hardware compatibility with a wider range of

products. In the case of Hyper-V, for example, as soon as Windows Server 2008—the general-purpose

operating system running in the parent partition—supports a particular type of hardware, then

Hyper-V supports it also. Hyper-V “piggybacks” on Windows’ hardware drivers and the I/O stack.

The same can be said for XenServer, although its “dom0” runs Linux and not Windows.

VMware ESXi, on the other hand, handles I/O within the hypervisor itself. This typically provides

greater throughput and lower overhead at the expense of slightly more limited hardware compat-

ibility. In order to add more hardware support or updated drivers, the hypervisor must be updated

because the I/O stack and device drivers are in the hypervisor.

This architectural difference is fundamental. Nowhere is this architectural difference more greatly

demonstrated than in ESXi, which has a small footprint yet provides a full-featured virtualiza-

tion solution. Both Citrix XenServer and Microsoft Hyper-V require a full installation of a general-

purpose operating system (Windows Server 2008 for Hyper-V, Linux for XenServer) in the parent

partition/dom0 in order to operate.

In the end, each of the virtualization products has its own set of advantages and disadvantages, and

large organizations may end up using multiple products. For example, VMware vSphere might be

best suited in the large corporate datacenter, while Microsoft Hyper-V or Citrix XenServer might

be acceptable for test, development, or branch-ofﬁ ce deployment. Organizations that don’t require

VMware vSphere’s advanced features like vSphere DRS, vSphere FT, or Storage vMotion may also

ﬁ nd that Microsoft Hyper-V or Citrix XenServer is a better ﬁ t for their needs.

As you can see, VMware vSphere offers some pretty powerful features that will change the

way you view the resources in your datacenter. The latest release of vSphere, version 5, expands

existing features and adds powerful new features like Storage I/O Control. Some of these fea-

tures, though, might not be applicable to all organizations, which is why VMware has crafted a

ﬂ exible licensing scheme for organizations of all sizes.

LICENSING VMWARE VSPHERE

With the introduction of VMware vSphere 4, VMware introduced new licensing tiers and bun-

dles that were intended to provide a good ﬁ t for every market segment. VMware has reﬁ ned this

licensing arrangement with the release of VMware vSphere 5. In this section, I’ll explain how

the various features that I’ve discussed so far ﬁ t into vSphere’s licensing model.

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