http://www.infoworld.com/article/07/09/26/Ghost-servers-that-haunt-your-bottom-line_1.html

The problem may not rival the movies Poltergeist or The Amityville Horror for sheer terror, but CIOs and datacenter managers are still well advised to deal decisively with so-called ghost servers. Like celluloid zombies, these forgotten pieces of equipment are dead when it comes to improving the bottom line, but they are very much alive when it comes to eating up IT budgets.

The unproductive — and usually undocumented — servers take up valuable real estate, consume increasingly expensive electricity and, in some cases, absorb ongoing maintenance and lease payments.

“You can find ghost servers in a lot of enterprises,” says John Phelps, an analyst at Gartner. “And the larger and more diverse the company, the harder it can be to have a single group or technology platform that provides control over all corporate assets.”

Sun Microsystems, through case studies of two large corporate datacenter operations and anecdotal analysis of efforts with many customers, believes that 8 percent to 10 percent of all servers in large corporations have no identifiable function. In the two datacenter studies, 150 ghost servers were found in an installation of 1,800 servers, and 354 ghost servers were found in an installation of 3,500 servers.

As the server infrastructure grows (virtual or physical) managing the asset as well as everything around it gets more complicated. Take any large data centers with blades and rack servers, and I’ll bet you’ll find at least one server which is either not in use, or not actively doing anything. Taking your asset list, your server inventory, working out what’s doing which role and where it is can be a very effective way of freeing up data center space - that Compaq Proliant 1850 with 256MB ram running NT4 - you sure it’s being used? But keep in mind that sometimes those tier one servers can be the ones that no one has heard off - 68945 particularly if it’s never been rebooted or had an issue.