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A few day ago Bhargavi Srivathsan publishes a post in the Open Data Center Alliance website fostering an interesting discussion about comparison between Private Cloud and Public Cloud. This discussion was going to be analyzed in detail in ad-hoc panel in the Forecast 2013, on June 18th. Unfortunately I could meet that panel (I’m based in Spain), so maybe other ideas were added to the ones stated by Bhargavi in its post (in fact, the idea of Bhargavi was to warn and prepare the discussion in Forecast 2013).

I disagree with some of the point that Bhargavi said in its blog. So let me first copy the main Bhargavi’s paragraphs:

What is a Private Cloud? It is a complete cloud infrastructure that is dedicated to the needs of a single organization, typically implemented within the firewall of the organization employing internally available resources and controlled by the IT department. Now, how is this different from a public cloud? In a public cloud, the services are delivered over a network that is open to public access and data travels through an un-trusted network.

So is private cloud better than public cloud? It depends. There is definitely a choice to make. While private and public clouds share several architectural similarities, there are clear differences. A private cloud solution comes with the following advantages:

  • Better control over data (and data security)
  • Ability to balance and provision resources with very little turnaround time
  • Better risk control

Obviously, there are some disadvantages in choosing a private cloud. Private clouds generally more costs upfront – there are costs associated with maintenance, planning for redundancy to avoid data loss, involving additional personnel to handle all operations in-house.

So let me show my opinion about:

First, according to NIST Cloud definitions, Private Cloud could be operated for the same organization that uses it (as Bhargavi stated) but also for an external provider (e.g., we offer that services to our Customers).

Second, in order to be a real and authentic Cloud it should be mutitenancy (NIST definition again), that implies that the Private Cloud, although dedicated to the same company/organization, the infrastructures are shared between different department of that company: each one of them becomes a different tenant; evidently, usually, that implies big companies (see Note 1). So, in general, the “ability to balance and provision resources” is not a difference with the Public Cloud: this issue is roughly the same in both Public and “real” Private Clouds. However, I agree with the other 2 points a Private Cloud offer both better control over data (and data security) and better risk control that Public Cloud.

Finally, I also agree with Bhargavi that one disadvantage of the Private Cloud is the price: it’ll be more expensive than the Public Cloud either you own it, or you uses the services of a provider; part of the facts for that are the ones Bhargavi said, but for me there’s one more important (because, in some way, it is mostly the root cause of them): in spite of a real multitenant (departments of a large company) the usage percentage of infrastructures of Private Cloud will be, in general, lower that the Public Cloud usage percentage, so the Public Cloud prices can be cheaper because of the better usage of infrastructures, better usage of technicians operating the cloud, and so on.

Note (1): For not large enough companies the “Community Cloud” could be the answer if “private” approach is needed; in this model, according to NIST definition, the cloud infrastructure is provisioned for exclusive use by a specific community of consumers from organizations that have shared concerns, e.g., mission, security requirements, policy, and compliance considerations; besides, as in the case of private cloud, the cloud may be owned, managed, and operated by one or more of the organizations in the community, a third party, or some combination of them, and it may exist on or off premises).