MAINFRAME AND high-end Unix server administrators have long relied on the ability to logically partition systems in order to distribute application workloads and make efficient use of pricey hardware. The partitioning technique, or server virtualization, introduces a software layer that effectively enables multiple, independent operating environments to make use of a single set of static resources.
Server virtualization offers an opportunity for companies to stretch IT dollars through more complete utilization of available processor cycles, and to substantially reduce hardware costs through server consolidation. But mainframe-class partitioning for Intel-based systems has for years been little more than an aspiration. Now, as lower costs become increasingly critical for customers, vendors in this niche are finally innovating.
One of the trailblazers in Intel-based server virtualization has been VMware, a relatively young startup that has impressed me during the past several years with its product line. Its entry-level VMware Workstation and GSX Server run atop your existing OS to create multiple virtual machines, each capable of running the gamut of Microsoft OSes -- from DOS to Windows XP Pro -- as well as Linux and FreeBSD.
VMware's crown jewel, the ESX Server, creates its own host operating environment, providing dynamic memory allocation, solid resource management, and provisions for the independent management of processor workloads in SMP (symmetric multiprocessing) environments. ESX Server provides good portability, allowing administrators to easily move and reallocate virtual environments as workloads dictate.
The success of VMware has caught the attention of major vendors including IBM and Sun, both of which are announcing server virtualization capabilities of their own in upcoming products. IBM is looking to capitalize on server virtualization in its eServer xSeries architecture, on which VMware's ESX Server has already been optimized to run. And Sun is making virtualization part of its forthcoming Solaris 9 OS, although its approach varies slightly from that of IBM and VMware.
Solaris 9 will allow administrators to run multiple partitions within a single Solaris service container. Although it won't run multiple operating systems, the single container will maintain independent resource allocation and monitoring across multiple partitions.
There are, of course, downsides to server virtualization. An outage on a single system risks bringing down multiple processes in one fell swoop. And, asking for vendor support of applications not running in a "clean" OS environment might be thorny. But for many applications these risks are acceptable.
If your server farms have become unwieldy and you can stand to save a few bucks by improving existing resource utilization, the virtues of virtualized server consolidation are worth exploring. It's not just for mainframes anymore.
Are you using server virtualization? Share your experience by writing to me at firstname.lastname@example.org.