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What kinds of challenges does virtualization present?

This technology changes the way a data center is managed, administered and operated. For example, before server virtualization, you could walk into any data center, ask the admin to name the organization's top five applications, and he would be able to show you the machines those apps were running on. However, the traditional coupling of hardware and software is broken by virtualization.

This decoupling creates the potential for performance conflicts. For example, some applications have cyclical performance profiles. A West Coast stock-trading application and a SIMEX app running on the same machine are going to overlap at peak market hours, slowing performance. Consequently, administrators have to think through how the virtualized data center will operate. The major virtualization vendors typically provide extensive technical resources and at least some training to explain how their solutions work. But each data center operates differently, and it's up to the administrators to know their systems.

What should I look for in a virtualization solution?

In a word: management. The core hypervisor technology that decouples the application stack from the underlying hardware is well on its way to commoditization. The large enterprise software vendors (Microsoft, Sun Microsystems, BEA Systems, Hewlett-Packard, BMC and CA, for example) are including it in their product suites, and the standalone virtualization vendors are giving it away. Where they differ is in their ability to provide tools for managing, monitoring and optimizing the allocation of virtualized resources. Look for solutions that provide easy-to-use tools for gathering statistics and applying dynamic policies to better allocate your physical resources among the virtual consumers of those resources.

Consequently, the innovation in the virtualization space is happening up the stack. The next-generation products are all about management. VMware has seen the writing on the wall, and has made the shift. Its VMware Infrastructure suite puts everything—servers, storage and the network—into a single resource pool. These enterprise virtualization solutions, such as VMware's ESX Server, blend CPUs, memory, networking, storage and applications into seamless pools of computing resources.

Virtualization can go a long way toward reducing the physical requirements of the data center, but it can also compound the level of management complexity of those servers. So look for solutions that provide cross-platform systems management for both the virtual and physical machines.

Also, you'll want the ability to migrate your organization's legacy applications and existing operating systems, without modification, onto virtual partitions. This migration should make it simpler to enhance the performance of those applications, but you'll need a solution that supports the integration of virtualization with legacy management tools.

Virtualization is no longer just about server consolidation. Flexibility is another key benefit of the technology. In virtualized environments, it's easier to move things around, to encapsulate, to archive and to optimize. The leading virtualization vendors are providing "live migration" capabilities that make a network administrator's life easier and more productive.