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Implementing Virtualization: Page 5 of 7

Moreover, the Xen hypervisor itself remains an open-source project with a large industrywide community following, and a growing number of companies have chosen to adopt and build on Xen technology. Virtual Iron, an early Xen adopter, has been around for more than four years and originally offered Linux virtualization via the use of its own VFe hypervisor technology. But with the introduction of Xen 3.0, Virtual Iron scrapped VFe, embraced open-source, and shifted its development energies to what it considered most important: Management of the virtual environment.

Rather than loading its management-system software on each physical server, as VMware does, Virtual Iron places a small, bare-metal version of the Xen hypervisor on each system and incorporates a separate, dedicated server to provide resource management services to all systems in the hardware pool. The Virtual Iron management server automatically builds an inventory of all physical devices in the attached servers and enables creation, resource allocation and deployment of virtual servers anywhere within the virtual infrastructure. With features like policy-driven workload management, dynamic capacity provisioning, extremely fast VM migration, and advanced tools for reporting and analysis, Virtual Iron is looking to offer the enterprise-class management tools that Xen-based systems formerly lacked.
Another major buy-in to the open-source Xen hypervisor technology has been from companies like Red Hat with Enterprise Linux 5, and Novell, which now offers enterprise-class high-level management, support and certification of Xen-based VMs under SUSE Linux Enterprise 10. Being an open-source virtualization effort from the beginning, the rest of the Linux community has pretty much been on board with Xen from the start, and Xen-based virtualization can be used with many of the Linux distros currently available.

We recently reviewed XenSource's XenEnterprise (find our article here).

Microsoft

The 2004 release of Virtual Server 2005 marked Microsoft's entry into server virtualization, but the company received mixed reviews, in part because Virtual Server lacked good management tools and services. Now back as Virtual Server 2005 R2, the product has been seriously revamped; it's obvious from the long list of improvements that Microsoft has heeded the cries of IT pros in the trenches. VSR2 (Virtual Server 2005 R2) will require installation of a stripped-down, core version of Microsoft Server to manage a virtualization stack and provide device support for guest OSes. The core OS allows VSR2 to use all hardware devices normally supported by Windows Server and creates a uniform hardware platform for spawned VMs.

This latest version of VSR2 was designed to take full advantage of VT-x and AMD-V instructions. Also new in this release will be the System Center Virtual Machine Manager, a standalone application chock full of centralized management tools to offer simplified system migration, intelligent provisioning, scriptable automation and rapid system-recovery capabilities. The emphasis of VSR2 will continue to be Windows-specific virtualization, but it looks like Microsoft has learned to work and play well with others—at least in this area—and has begun to provide VM add-ins and technical support for Linux guest OSes. VSR2 will also support VMs running older versions of the Windows Server platform, such as Server 2000 and NT 4.0, a real boon for those chained to legacy applications.

The next step for Microsoft will be Windows Server virtualization (WSv), a hypervisor-based virtualization technology planned for Windows Server 2008 (the OS formerly known as Longhorn). The first generation of WSv is expected to ship as a service pack within 180 days of the official Q1 2008 release of Server 2008, but some anticipated high-level features, such as Live Migration and dynamic resource allocation capabilities, will not be available until even later.

From a practical standpoint, all of these vendors are moving in the right direction, and we think the proper emphasis is being placed on the problems associated with converting physical environments, dynamic resource allocation, seamless migration of VMs and protecting VMs from one another. But virtualization also raises some application-level issues that don't come up in conventional server environments, for example: