Introduction

Currently CloudStack has following 3 deployment planners available out-of-the-box:

• FirstFitPlanner
• UserDispersingPlanner
• UserConcentratedPodPlanner
• BareMetalPlanner

Each of these planners implements some heuristics that provide ordering of resources on some basis, while choosing resources for VM deployment. All the planners work on the available set of resources in a given datacenter that are shared across various accounts.

Currently in a CloudStack deployment, only one of these planners is used for VM deployments. The global parameter 'vm.allocation.algorithm' decides which planner will be used.

But if deployment planner is exposed per ServiceOffering then multiple planners can co-exist.

In such case, we will need resource reservation between planners, so that planner executions do not step onto each other's resource choice.