Sumit Sharma

When would you choose a Public Cloud over a Private Cloud?

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Choosing whether to host a service on a private cloud, or procure it from a public Cloud depends on where the service lies on this spectrum. Services that are critical to differentiating the business will not be easily publically available, moreover, there are likely to be heavy compliance, security and governance restrictions which public Cloud service providers may not currently offer, though over time this may change as demand increases and public Cloud service providers evolve their service standards and agreements. In theory it could be possible to composite services and leverage the diversity of the greater ecosystem to source disparate services in a piecemeal fashion, and aggregating them through a Cloud brokering service who could potentially composite the service tailored to a particular business requirements. However this will require standardization of Cloud interoperability interfaces, metadata and other Cloud related architecture standards and protocols which all are a work in progress to say the least. Given this, such services are potential candidates for private Clouds, however there are still other factors such as economic return, technical and organizational feasibility and other risks and controls that need to be considered.

One could instinctively think that Services which are on the commodity end of the spectrum are strong candidates to be sourced from the public since they are heavily standardized and reusable. This is a fair assumption in many cases; however there will be cases where concerned data and information is business and security critical. In such cases, services would be potential private Cloud candidates.

Aside from analyzing the spectrum of services, network latency may be an issue to consider, depending on the geographic footprint of the organization concerned. Performance is paramount, especially with applications that have to send and receive a great amount of data, and in many cases the latency of the Internet is not acceptable in which case public clouds will not be a viable option.

Some argue that in reality a private Cloud won’t be able to match the elasticity of a public Cloud since it will be restricted to a smaller set of systems, especially given the risk aversion of various business unit and IT managers within the enterprise, as well as the cost benefits varying across the various business uses and IT. In theory this may be true however in practice, we don’t believe this should pose a problem if capacity planning and all other requisite process workflow automation is in place.

One drawback that should be considered is that a private Cloud infrastructure stack needs to be distributed across a heterogeneous environment of many different types of business units and systems, each having their own SLAs. So, as complexity of the environment increases, greater caution (and cost) is needed to manage the private Cloud environment and as more internal customers start to migrate towards the internal Cloud, management of the increasing demands becomes an ever more critical issue.


Written by Sumit

September 26, 2010 at 10:03 am

Posted in Cloud Computing

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