While the company is making inroads against Microsoft (NASDAQ: MSFT), Whitehurst still sees Red Hat's biggest growth coming from the UNIX-to-Linux migration customers. "I'll certainly say we are seeing more progress against Windows than we were a year ago," Whitehurst said. "I think as people get more comfortable with the product and we get a chance to demonstrate that broader value proposition, certainly it's an increasing mix of Windows [customer wins], but still that would be in the minority of business."