For instance, using such tools as BMC Software's Topology Discovery, EMC's Application Discovery Manager or mValent's Integrity, an IT manager could perform an ongoing discovery of the environment and track how virtual machines have changed. Manual efforts couldn't keep pace with the configuration changes that would occur because of, say, VMware VMotion or Microsoft Live Migration technologies. "IT has to stay on top of a lot more data in a much more dynamic environment," O'Donnell says.
3. Plan for capacity
Just because virtual machines are faster to deploy than physical ones, the task shouldn't be taken lightly. "If you are not careful, you can have a lot of virtual machines that aren't being used," says Ed Ward, senior technical analyst at Hasbro. He speaks from the experience of supporting 22 VMware ESX host servers, 330 virtual machines, 100 workstations and 250 physical machines.
To prevent virtual-machine sprawl and to curb spending for licenses and power for unused machines, Ward says he uses VKernel's Capacity Analyzer virtual appliance. It alerts him to all the virtual machines in his environment, even those he thought he had removed.
"There are cases in which you build a virtual machine for test and then for some reason it is not removed but rather it's still out there consuming resources, even though it is serving no purpose," Ward says. "Knowing what we already have and planning our investments based on that helps. We can reassign assets that have outlived their initial purpose."
When they create virtual machines, IT managers also must plan for their deletion. "Assign expiration dates to virtual machines when they are allocated to a business unit or for use with a specific application; and when that date comes, validate the need is no longer there and expire the resource," Forrester's Staten says. "Park a virtual machine for three months and if it is no longer needed, archive and delete. Archiving keeps options open without draining storage resources or having the virtual machine sitting out there consuming compute resources."
4. Marry the physical and virtual
IT managers must choose the applications supported by virtual environments wisely, say experts, who warn that few if any IT services will rely only on the virtual infrastructure.