The legacy of Paul Maritz as CEO of VMware is that he ushered it from its startup phase as inventor of x86 virtualization into contention to become a dominant next-generation tech vendor. It wasn't easy.

He became CEO in July 2008. At the time, many expected VMware to fail--another startup whose market was taken away from it by an established powerhouse, Microsoft. Maritz had been preceded by Diane Greene, a Berkley-trained computer scientist who proved to be a no-nonsense but approachable CEO, who could be counted on to translate the technology of her brainy husband, chief scientist Mendel Rosenblum, into software products.

Whatever doubts virtualization users may have had about the technology, and they had some, they trusted Rosenblum, Greene, and their fellow co-founders. VMware had a meet-the-founders, we're-all-part-of-the- family feeling for the early adopters attending VMware's annual user group meetings. If anything went wrong, Greene would own up to it.

In July 2008, Greene was out, at the direction of EMC, the new owner of VMware, and Paul Maritz, a tested veteran formerly at Microsoft, was in.

Microsoft was preparing to give away server virtualization software, by including a free hypervisor, Hyper-V, in Windows 2008 Release 2. Microsoft System Center, already well established in the data center as Windows Server system management software, was getting a new module, Virtual Machine Manager. Many expected Microsoft to take over the x86 market for virtualization software. Six Reasons Why Microsoft's Hyper-V Will Surpass VMware was the title of one analyst's report issued six days before Greene was dismissed.

It didn't happen, largely because of Maritz.

[ For more analysis on the executive changes at EMC, see VMware, EMC Shakeup Hints At Data Center Future. ]

Maritz instinctively understood the trust that CIOs were investing in VMware. As long as VMware drew an ambitious road map, told customers what it would bring to their data centers via virtualization, and delivered, CIOs would continue to look to VMware for their future data center software.

VMware didn't rest on the ESX Server hypervisor. VMware drew bigger and bigger pictures of what ESX Server's supporting cast--vSphere 5, VCenter Operations, vCloud Director--could do. Then, as Maritz emphasized in one interview with me, "you have to execute." As long as VMware delivered, companies would be reluctant to rip out their VMware deployments that were installed and working in their data centers.

A poll by Veeam's V-Index web site toward the end of 2011 found two-thirds of virtualization users considered ESX Server their primary hypervisor. There was a bitter contest going on in the market, but it was between Microsoft (16.4%) and Citrix Systems (14.4%) for second place.

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Some observers thought those figures were too low. Michael Dell, a close partner of Microsoft and VMware, told attendees at Dell World in Austin last October that 80% of Dell's customers who were using cloud computing were interested in moving VMware workloads to the cloud. Dell announced his company was partnering with VMware to produce its cloud computing products.

Maritz knew that Microsoft, while formidable, had numerous battles to fight and a limit on the resources that it could pour into virtualization. If VMware kept its head, focused on its roadmap and executed, it would be hard for Microsoft to catch up.

Having led the consolidation of servers in the data center, Maritz used that stronghold to pivot into managing virtualized servers and bringing other virtualized resources in storage and networking into the fold. On top of that, VMware added systems management from the point of view of virtualization as the new control point of data center resources. It was tough for the traditional systems management vendors, including Microsoft, to keep up.

It was Maritz's unflappable sense of direction at this stage of VMware's development that brought VMware to the point where it's nearly a $5 billion a year company, adding $1 billion in new revenues the past year.