VMware will also have to overcome concerns that enterprises have about security and performance. Those are the first two issues customers ask about when discussing cloud services, said Savvis CTO Bryan Doerr.

Savvis unveiled a pay-as-you-go computing service Tuesday, based on vSphere, that it calls Project Spirit. Similar to Terremark's offering, customers will go to a Web portal and be able to provision servers, storage and firewalls with a drag-and-drop interface. Savvis will offer three levels of service depending on the levels of security and performance customers want to pay for, Doerr said. It posted a about the service on the Web and said a beta would launch later this year.

IDC analyst Jean Bozman said vendors are eyeing cloud services because they are a bright spot in an otherwise bleak IT spending environment. They are also important to VMware as it tries to maintain its technology lead against rivals Microsoft and Citrix Systems, she said.