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It’s War: Public vs. Private

(UPDATED: Added link to Adrian’s blog where he expands on his twitter question)

I have been asked this question a couple of times in a couple of days, so that always warrants a blog post.

The question first came up in a webinar I did with rackspace last week, it featured in regular conversation at Cloud Connect and then again on twitter from Adrian Cockcroft. The questions is framed like;

  • “There is no technical reason for private cloud, its all $, FUD, and internal politics. Discuss.” – Adrian Cockcroft,
  • Do you think there is a need for private clouds (vs. public)?

Important to note we are not talking whether they should run on a cloud. This argument only applies to applications & workloads that have already been determined to be a good fit for cloud.

The latter two are fairly easy to understand because they relate to the diversity organization requirements unable to be serviced by a commodity service, or the natural inertia of organizations to adopt new methods. The arguments cover a range of topics, including;

  • trust,
  • service level agreements,
  • security needs,
  • migration costs,
  • and many more.

The more meaty argument is Adrian’s. Is there any “technical reasons” for not running on public cloud? This challenges us to try and determine if there are architectural patterns that public clouds cannot provide.

So, Adrian is royalty in cloud (I prefer royalty because it reflects respect for his achievement and position, vs. clouderati which reflects some sort of enlightenment), but his question is a little sensational. First of all it is so broad, it’s difficult to support or refute. Secondly, it encompasses the future, for which anything is possible. He blogs in more detail here.

But here is my logic. Public clouds are designed on one basic premise that differentiate them from a private cloud, “Economies of Scale”. Having enough workload running in a multi-tenancy environment will balance out noise in the elasticity of workload and also drive down costs for the operation of the infrastructure. So for a private cloud to exist technically, it needs;

  • enough volume to have economies of scale internally,
  • workload elasticity to warrant a cloud,
  • a specific technical requirement that does not warrant economies of scale publically,

So, I am an architectural pragmatist. Sometimes the cloud debate gets a bit more religious and I feel more like an atheist or a nialist. I do believe that infrastructure (compute, storage, network & operating systems) and the workloads it is able to support are sufficiently complex to represent a distribution curve of requirements. The amount that can be served by public clouds represents the meat in the middle of the curve. This curve might have an extremely narrow peak, but the tails still exist.

The argument will be that there are many different public clouds, and they can service a wide range of technical requirements, but I still believe that the underlying architecture patterns are complex enough to reveal patterns that cannot be provided in volume.

The other issue I have with economies of scale solutions is they inherently develop lowest common denominator architecture. The non-technical aspects of public clouds limit their ability to solve for all workloads.

In closing, I will try and give examples of workloads that need private clouds:

  1. Slot machine gaming software – very elastic workload with very specific technical requirements for security, auditability and physical machine interface. I cannot see this be a public cloud.
  2. Online gaming – take a large facebook based games company. Lots of elastic workloads, but very close correlation architecturally to each other. They have the economies of scale alone to get the benefits of efficient operations. I can see them developing a private cloud that is optimized for their technical requirements and provides high degrees of automation to get better efficiencies than a public cloud.

What do you think?

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Brad Vaughan is a twenty year veteran consultant working with companies around the globe to transform technology infrastructure to deliver enhanced business services.