I think many IT professionals realize that many application performance issues eventually boil down to storage and physical I/O. That was true before server virtualization, and it's certainly true now.
Storage array vendors do what they can. Operating system, hypervisor and database vendors do what they can as well.
But between the two, there's the potential for a smart layer of storage software that does what others can't.
As an example: way back when Solaris was popular, Veritas' VxVM and VxFS were almost ubiquitous. Both products offered an important value-added layer than neither the host OS nor the storage array did well. As a result, the Veritas products become almost a de-facto standard in an larger Sun environments.
While I was exploring Virsto (recently acquired by VMware), I was struck by similarities to what Veritas did years ago. It's clearly a smarter storage abstraction layer than either the hypervisor or the array can provide on their own.
The real question — now that Virsto is owned by VMware, will Virsto technology end up being a de-facto standard for many VMware environments?