I must confess, I don't quite "get" the private cloud. Sure, it's a way of optimizing infrastructure, largely through virtualization. In that way, it's like the public cloud. But that's largely where the resemblance ends.
There's no multitenacy, because you're not serving multiple customers and thus don't need the ability to isolate customer-specific traffic, data and configuration of resources. (Unless, of course, you want to treat your business units that way.) Because it is limited by internal hardware and software, a private cloud lacks the massive scalability of a public one.
I take some comfort in the fact that I'm not the only one who is confused. Last month, IT Business Edge blogger Art Cole wrote about long-term doubts over the private cloud, pointing out:
... There's a growing chorus of voices arguing that the economics of the private cloud do not work. Not only are most enterprises too small to see any real benefit to manning their own clouds, but the security and reliability fears surrounding the much more cost-effective public cloud are overblown. Private clouds, therefore, entail all the costs of traditional infrastructure but deliver none of the benefits.
Add Vineet Nayar, CEO of Indian services provider HCL Technologies, to the list of skeptics. In an interview on the Horses for Sources blog, Nayar is largely dismissive of cloud computing. He says the public cloud makes the most sense for small companies that lack the resources for robust on-premise IT systems and for larger companies involved in application testing and other situations that require lots of scalability on a temporary basis.(Nayar was apparently more blunt in a presentation that preceded the interview, in which he described the cloud as "bullshit," according to Horses for Sources CEO and research head Phil Fersht.)
He's even more dismissive of the private cloud, calling it "a convenient way of shutting down any conversations around cloud." He says:
... everybody asks the CIO, 'Have you implemented cloud?' And the CIO gets away by saying, 'Yes,' when you call what you're rightly saying is an enterprise re-architecture of your internal data center as private cloud. ... Every board is asking for a cloud strategy. So you might as well have a private cloud strategy and call it a cloud strategy and get it over with and put a tick in the box and get on with life.
In his post on private cloud doubts, Art cites the opinions of some experts that experimenting with private clouds can serve a valid purpose by helping companies determine what is and is not possible in the public cloud. He writes:
Ultimately, then, it's probably best to look at the private cloud as a means to an end, rather than the end itself. Your goal is a working knowledge of cloud environments to help you better navigate the intricacies of the public infrastructure.
IT Business Edge blogger Mike Vizard made a similar point, noting that while many IT organizations are piloting internal private clouds running on top of internal IT infrastructures, many of those private clouds will end up running on external virtual infrastructures that are more efficient, cost-effective, and yes, even more secure than the internal ones.