Public Cloud in Private Cloud’s Clothing

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In yesterday’s batch of links I commented on James Urquhart’s video “Clarifying Internal Cloud versus Private Cloud.”

James Urquhart on Internal/External vs Private/Public clouds. While I agree that Private is not always equal to Internal, James’ [re]definition of increasingly accepted terminology just serves to muddy the waters by introducing the existence of unified control systems as a defining characteristic.

James called me on my comment, asking what I see the difference being.

Just as I finished typing the above words, Savvis’ Benson Schliesser jumped into the mix with his post “Cloud: Private vs Public, Internal vs External, Oh My!” adding an interesting dimension to the dialogue.

First off, my thoughts on James’ video. In the video he is making two points:

  • Internal/External is an issue of “ownership”
  • Private/Public is an issue of “control”

To illustrate the latter point, he provides an example of a unifying control system creating a “private cloud” from internal and external resources. This example is what I was primarily responding to, as it seems to label as “private cloud” an idea more commonly called “hybrid cloud,” primarily by virtue of the unified control system. This masks the “less private” (e.g. hybrid) aspects of the cloud and as a result (IMO) “muddies the waters.”

The notion of private vs public cloud remains central to the broader discussion around cloud computing, at least from an enterprise perspective. Right now, there a number of terms that seem to be used more or less synonymously to identify the same concept: private vs public, internal vs external, on-premise vs off-premise.

Most of the time, when I hear folks trying to subdivide this world even further, it comes as part of an attempt to sell “public” cloud offerings as “private” ones, to put it bluntly.

To extend James’ example, if I deploy a tool that allows me to “control” virtual resources from Amazon EC2 and GoGrid, either directly or via a broker, without having to utilize either offerings’ native tools, does that mean I’ve created a “private” cloud based on these “public” cloud services? Amazon would like you to think so. Most enterprises would not.

I define “private cloud” as a system exhibiting cloud characteristics, but operated for/owned by/contolled by a single organization. As mentioned in previous posts, I believe tenancy (an attribute that didn’t even figure into your list, Benson) is a key determinant of “privacy.” By tenancy I’m referring to who the cloud is “operated for.”

Ownership seems less important — if the system is physically owned by a third party but operated for my exclusive use (maybe even by me), that’s private. And control seems too hard to pin down — do I control EC2 since they give me an API? If you control a system for my exclusive use, but do so on my behalf (i.e. I control you, e.g. contractually), who is in control? (In other words, is “control” a transitive property?)

So Benson, to the point of Bryan’s quote, off-premise private cloud works fine for me. Shared private cloud, not so much. (The private cloud is shared among its users, yes, but not with other customers.) Shared clouds with better security measures and “enterprise grade” QoS are  perhaps “enterprise-grade public clouds” in my book (or maybe “virtually private” clouds).

In the trenches, of course, you’re absolutely right though. There are more than just a couple of defining attributes of cloud computing. And, in the same vein, we will measure each of the attributes with more than a single bit.

In the end, customers are smart, and the labels we put on our offerings will mean less and less as the market matures and educates itself.

1 comment
  • Krish

    Sam, I agree with you that “tenancy” should be part of the defining attribute for private clouds. You nailed it with a great example.

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