Is “Cloud Bursting” a Reasonable Scenario for Hybrid IaaS?

When people list use cases for “hybrid cloud computing” the “cloud bursting” scenario is nearly always trotted out first.  But is bursting really so desirable?  Here’s my answer first, followed by the explanation:

  • For IaaS? NO
  • For PaaS? YES

I think bursting gets prime-time coverage because it represents perhaps the most disruptive use case for hybrid cloud computing – the ability to augment your own data center’s compute power by harnessing other capacity (public cloud, other private clouds, etc.). But the devil is in the details, and an explanation of how that augmentation is actually achieved is usually a hand-waving exercise.

Since we’re probably talking IaaS deployments, then a brute force method of achieving cloud bursting would be migrating “workloads” between cloud hosting targets – something similar to cold migration of VMs between hypervisor hosts.  But migration across WAN links, as would be probable in this bursting scenario, is vastly different from the relatively lightning-fast migration (cold, warm, or live) available with, say, an ESX cluster. Clearly, some form of optimization is required.

And then we start talking about compression and de-duplication and WAN optimization – all of which try to mitigate the real underlying problem: IaaS-type VMs are simply not the right choice of container to achieve truly scalable and efficient bursting solutions. I contend the ultimate “optimization” for workloads that will enable them to move at will between cloud hosting targets is the “PaaS-ification” of them.

To take full advantage of the hybrid model, applications must be designed with that model in mind.  Distributed execution and data access are more recent tenets in programming, requiring more thought and planning.  Most applications in private data centers are born of simpler, but less flexible architectures.  To their credit, IaaS-type VM’s are an effective way to salvage legacy applications in the early years of the cloud revolution.  But they’re inefficient, blunt instruments for achieving cloud bursting.  Yes, cloud bursting for IaaS will be implemented, but it will have limited value and eventually be eclipsed by more PaaS-like implementations. No application will fully realize the benefits of hybrid cloud deployments – bursting included – until it has been re-written specifically to take advantage of it.


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