Interestingly, many shops are buying Microsoft's Datacenter licenses and assigning them to physical servers running VMware vSphere. Those licenses allow for unlimited Windows Server 2008 R2 VMs on that host, even if it's not running Hyper-V.
Citrix XenServer is priced per server, regardless of server capacity. Like VMware, Citrix offers a choice of several tiers. Red Hat Enterprise Virtualization is the simplest (and cheapest), with flat per-year subscription pricing per physical server based on 9-to-5 or 24/7 support starting at $499 per server per year.
Virtualization now, more than ever The major excuse for delaying a virtualization project in the past was the price of VMware balanced against the lack of significant features such as live migrations, high availability, load balancing, and even guest OS support in competing products. That is no longer valid, as each solution capably demonstrated these features. Larger infrastructures may still view virtualization as VMware and VMware only, but the smaller and midrange shops that can live without VMware's advanced features suddenly have a plethora of options. They can still bring the extreme benefits of virtualization into the data center and not bust the budget.
Among the three challengers, Microsoft Hyper-V comes closest to VMware vSphere in overall management functionality. However, whereas VMware, Red Hat, and Citrix combine virtualization host and VM management in a single management server, Microsoft spreads the functions across multiple System Center tools. Hyper-V's advanced capabilities come at the cost of additional overhead, configuration, and complexity for administrators.
Citrix XenServer combines great Linux performance, rapid deployment, and the major advanced features, though high availability and load balancing require supporting players and additional configuration. A significant drawback is that all VM management operations are serialized. It takes significantly longer to perform any action (such as power up or power down) on multiple virtual machines in XenServer than in any of the other solutions -- a limitation that impacts both manageability and scalability.
Red Hat Enterprise Virtualization has all of the essential management capabilities, but they're nowhere near as complex to implement as the tools for Hyper-V. RHEV also has a few rough spots, including odd gotchas in host maintenance mode and high availability, but it boasts a quick install, solid Linux and Windows performance, a good CLI, and advanced memory management features such as page sharing and compression. It comes closest to VMware in having all the ingredients to support a scalable environment.
It may come as little surprise that VMware vSphere still leads the pack by a handy margin, but the gap is closing fast. If there's one obvious result of this test, it's that there's never been a better time to shop for a virtualization solution.
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