Cloud bursting is an application model where an organization can utilize the compute resources of one cloud and burst into another cloud when the demand for compute resources exceeds the limit allowed in the current cloud. Thereby, cloud bursting allows organizations to seamlessly handle excess workloads; while, paying for the additional computing resources only when they are needed.
Private PaaS uses two smart deployment policies to handle cloud bursting: Auto-scaling policy and Deployment policy. For example, if we define a deployment policy that has two cloud providers: OpenStack and EC2. In the policy we can define the auto-scaling algorithm that needs to be used. For the purpose of cloud bursting, we can choose the “one after another” algorithm. Thereby, when the workload increases and one cloud (e.g., OpenStack) reaches its maximum capacity, it will scale into the next defined cloud (e.g., EC2), so that the required additional compute resources can be leveraged from another cloud provider or even via another cloud that belongs to the same cloud provider. In Private PaaS, the following are the typical cloud bursting scenarios:
- Cloud busting from a private cloud into a public cloud - For example, cloud bursting from a OpenStack cloud, which has been deployed on-premise, to an EC2 cloud, which has been deployed publicly.
- Cloud bursting from one private cloud into another private cloud - For example, cloud bursting from one OpenStack cloud to another OpenStack cloud where both clouds have been deployed on-premise.
- Cloud bursting from one public cloud into another public cloud - For example, cloud bursting from an EC2 cloud into a Rackspace cloud where both clouds have been deployed publicly.