Virtual machines free operating systems from underlying computer hardware, so one physical server can host multiple versions of Windows and Linux, map to limitless external data stores, and offer an endless variety of applications while being managed from a single console. There's a catch, of course: If management isn't your strong suit, VMs can spiral out of control and put data at risk.
Technologies such as VMware's VMotion let "guest" operating systems migrate from host to host in real time as business needs dictate, while providing relatively simple and inexpensive failover, clustering, and scalability.
With forethought, virtual servers with complementary usage loads can comfortably share the same physical platform. An enterprise-class server running multicore processors optimized for virtualization (AMD-V, Intel VT) can easily host five, 10, or more guest operating systems.
CONTROL AND EXPOSURE
Problem is, even magic bullets can misfire. The ease and speed with which virtualized servers can be deployed on a host platform is tempting some IT pros to bypass the formal, established change-control processes most organizations have in place. Don't do it. It's too easy to deploy a noncompliant guest server on a host running mission-critical production VMs, increasing risk. When VM-specific security policies are lacking, plan/build/run disciplines are abridged to launch/run/pray.
Traditional safety nets in the form of IP-based security tools may be ineffective because VM communications within a host server never venture onto the physical network. VMs could be at risk of attack from a compromised guest.
The answer is to remember that a server running as a VM is still a server, with all the requisite maintenance and management requirements. IT shops have never had this level of flexibility and creative control in client-server environments, but we've also never had this level of exposure.
While traditional operations center management vendors are upgrading their products to support virtualized machines, new entrants such as Cirba are releasing analysis and management software targeting VMotion environments.
Still, VM management is a dynamic market at the moment. Look for Microsoft and VMware to bundle in more management tools as their platforms mature. Near term, investigate new players in this space if you're planning a large-scale VM deployment in the next year.