VNX and VNXe sales have been good, says EMC's Herzog. But NetApp is growing; in 2010, it rose from sixth to third place in overall storage revenue as its sales increased 51 percent. Although the major research firms don't measure the unified storage market by itself, NetApp is said to dominate it. Pillar Data Systems, a specialized vendor, is recognized as a technical pioneer in unified storage, while Hewlett-Packard and Dell are pursuing their own approaches to the technology.

However, EMC remains the world's largest enterprise storage vendor with 26 percent of the market as measured by factory revenue, according to IDC (a sister company to CIO's publisher). And EMC's ability to repeatedly transform itself--as with its embrace of cloud technology and its move toward virtualization with the VMware acquisition--is a core strength, says Peters. Meanwhile, EMC has also used its market presence to draw attention to unified storage, which, Peters adds, needed "the blessing of an industry giant."