"When you have an online program running in-house, you have to make sure the uptime is high enough so professors and students can do their jobs," says Praneeth Machettira, online technical director at Suffolk University's Sawyer School of Management. "Virtualization came in as a way to do disaster recovery."

The school used ESX Server from VMware Inc. in Palo Alto, California, to create a set of five virtual machines running on ProLiant servers from Hewlett-Packard Co. But although using virtual servers provided some redundancy, it wasn't enough. A standard backup application wasn't adequate either, because of problems with open files and CPU spikes. So instead, Machettira went with Double-Take from NSI Software Inc. to provide full replication in real time of everything taking place on the virtual servers.

"The typical load balancing, clustering and tape backup is not enough," says Machettira. "But by using a combination of virtualization and replication, when a server goes down, we can have Blackboard back up and running in three to five minutes."

A different animal

Server virtualization is cropping up just about everywhere these days. According to IDC, more than three quarters of companies with 500 or more employees use virtual servers, and 45 percent of all new servers purchased this year will be virtualized. Once limited to mainframes and large Unix boxes, the technology is now moving into two- and four-way Linux and Windows servers.