Cloud bursting means workload moves from one cloud to another on the fly. With differentiation of public cloud and private cloud, you can have 4 different permutations: private to public, private to private, public to public, and public to private.
What people talk about the most is the case of private to public cloud. Think about the case in which an enterprise suddenly has more workloads than its infrastructure can handle. It’s very natural to move some of the workloads to one or more public clouds.
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To achieve a successful cloud bursting, you will first need to move the workload. If it’s a virtual machine, just vMotion or simply copy the virtual machine files. After the workload up running in the new cloud, you need to route the traffic to it, for example using a load balancer. From users’ perspectives, they don’t feel they are using other clouds.
Overall I think cloud bursting is great in theory, but based on a hypothetical assumption about the enterprise workloads.
First, most enterprise infrastructure is under-utilized. As Carter Shanklin pointed out in his tweet, “What’s all this talk of cloudbursting? Aren’t datacenter utilization rates still generally below 10%? Figure out how to use the 90.” Well said! When your datacenter is not fully utilized, there is no point to burst outside.
Secondly, unlike Web 2.0 companies, enterprises don’t normally see erratic workload patterns. I’ve heard a Web site needs 1,000 servers over a weekend but just several during weekdays. In that scenario, you do get a lot of saving by bursting into a public cloud. For a typical enterprise, the types of workloads are mixed and they can offset each other from time to time. You can also schedule these workloads some times. Even occasionally you cannot, the increase will never be as dramatic as several times or hundreds of times as Internet companies. With this in mind, I do think Internet companies need cloud bursting. Or, why bother with bursting? Just live wholly in a public cloud!
In conclusion, I don’t think cloud bursting has arrived its prime time, maybe never. Instead of pursuing these cool projects, an enterprise should really focus on its private cloud. Also every business is different, so don’t be distracted by Web 2.0 companies.