Packing them in

Hand in hand with hardware consolidation comes increased utilization of current server resources. Before virtualization, IT departments tended to limit each physical server to a single application and operating environment, as multiple applications tended to conflict with one another. The result was often server sprawl and inefficient use of server resources. Congdon says running multiple virtual operating environments on each server has increased server utilization at Capital One from an average of 30 percent to as much as 80 percent.

After monitoring his VMware environment for two weeks, NewEnergy's Tisdale actually found that he could pack many more virtual servers onto a physical server than he originally thought '" in the high teens and low twenties, rather than seven or nine. "Users generally overestimate how much they're using a server, and the software vendors are conservative in estimating the memory needs of their applications," he says.

Virtualization consumes its own server resources, of course, which can take its toll on application performance, but users point out that the overhead is offset by running applications on more powerful servers and taking advantage of VM portability. Congdon says general response times have improved now that his applications are sharing much more powerful server hardware.

When application performance declines due to an overburdened server, Next Financial, a securities broker/dealer, simply moves the virtual application environment to a less busy server. "You just shut down the virtual machine, move its disk on the SAN from one LUN to another on the SAN, reattach it on the new host, configure the VM, and launch," says CTO Ismael Carlo. (The company isn't using VMware's VMotion management product, which can actually move VMs around on the fly without any downtime.)