The dark horse in this race is Oracle because of its recent acquisitions of Virtual Iron and Sun Microsystems.

Virtual Iron gives Oracle a robust suite of management tools, while Sun provides a hardware platform and Solaris operating system.

“They still have some work to do, it’s not exactly a drop-in replacement, but for Oracle infrastructure it could deliver a complete solution,” said Gaelen Schreck of Forrester Research. “Sun had a great management suite in xVM Ops Center, and Virtual Iron had perhaps the best Xen manager in the market,” said Gartner’s Thomas Bittman. However, VMware, Microsoft and Citrix are all horizontally focused. Oracle, on the other hand, is focused on the vertical stack.

“They’ll argue this point, but it’s true,” he said. “Their business is about making the application down through the hardware as well managed a stack as possible, so it’s a very vertically focused solution.”

Oracle VM was more of a defensive move to keep VMware and Microsoft out of Oracle enterprises. “The reality of the situation is, I’ve talked to maybe two companies that are using Oracle VM, and I’ve talked to more than 100 that are running Oracle on top of VMware,” said Bittman.

The question now is: Do you want to have Oracle manage its own stack completely, or would you rather have a horizontal solution like VMware where Oracle is just one of many applications?

The answer to that question could change in the coming months, depending on what Oracle decides to do with Virtual Iron and Sun.