The company first talked about its "virtual data center OS" last September at the VMworld show in Las Vegas. Earlier this year it christened the product vSphere and last month it was officially launched during a splashy event featuring John Chambers and Michael Dell.

Now the software is on sale. Starting Thursday customers can order any of the six different versions of vSphere, which range from an Essentials package for smaller businesses to an Enterprise Plus edition for large data centers. The software is also ready for download from VMware's Web site.

VSphere marks a big step forward from VMware Infrastructure 3, the company's existing product. VMware positions it as a "cloud operating system" that will allow companies to centrally manage servers, storage and networks in their data center as if they were one big computer.

The software includes updates to VMware's core hypervisor that should allow it to handle large databases and other more demanding applications. VSphere quadruples the amount of memory available to virtual machines, triples network throughput and doubles the maximum I/O operations to more than 200,000 per second, VMware says.

A new feature called VMware Fault Tolerance can create a live replica of an application on a different server that can be used in the event of a hardware failure. Also new is vStorage Thin Provisioning, which allows less physical storage to be allocated to a virtual machine, and Distributed Power Management, which can consolidate virtual machines onto fewer machines during periods of low usage.