Point of confession here - I don't really get private clouds. There, I said it. It's not that I don't get the value of virtualization or virtualized data centers. I absolutely do.
I think the challenge I have is two-fold -
1. What is the definition of a "private cloud"?
2. Is applying virtualization all that's required to legitimately deliver private cloud services?
To examine my connundrum, let's revisit my simplified definition of cloud computing which I blogged about previously -
"Cloud Computing is an on-demand delivery model for IT services or applications with the characteristics of multi-tenant hosting, elasticity (variable capacity) and utility based billing."
Regardless of whether you accept this simplified definition or think that it should include more, many would believe that this is the minimal set of what constitutes cloud computing. I'm not sure what typically passes as private clouds today actually fit that definition. As much as I believe in the benefits of virtualization, I'm not sure that simply applying it in a datacenter doesn't make for cloud computing - hence, not private clouds.
Virtualization does indeed allow for some variability in capacity but it is limited. And, the cost to expand that variability means additional capital expense for the company. That seems to run counter to some of the inherent benefits of cloud computing.
That's at the heart of what Amazon is addressing through its introduction of Virtual Private Cloud (VPC). Werner Vogels discusses this on his blog and goes as far as to say that "private cloud is not the cloud". From what I can tell Amazon VPC actually gets closer to the heart of what private cloud computing should be. Rather than regurgitate what Dr Vogels says, you can read it for yourself here. The point is that private clouds shouldn't mean on-premise clouds (whatever that means). Perhaps there's nothing wrong with a loose, minimalist definition of private clouds but I just wonder if it's really part of cloud computing.
Yet with technologies like Amazon's VPC and VmWare's vSphere, you can expect the private cloud arena to continue to evolve.
And, you'll want to stay tuned for those changes when they occur. In the meantime, help me out by weighing in and sharing your thoughts on private clouds. If you've implemented a private cloud, I'd love to hear your experiences too.
Hi Andre
For one, what you're saying makes sense... private clouds necessarily need to be 'private' in the way they manage data, and maybe even applications. It doesn't mean that the physical infrastructure needs to be within an organization.
But that's not to say that on premise clouds (or internal) don't make sense. Your definition works in that case too, just that 'billing' probably needs to be changed to 'tracking' or 'monitoring'.
Have a nice day.
Sujay