Placement Policy for Erasure Coded Containers

The default placement policy for Erasure Coded (EC) containers is SCMContainerPlacementRackScatter. This is currently the only supported Placement Policy for Erasure Coded containers. This tries to spread container replicas across as many racks as possible.

For an EC 3-2 container, there will be one replica per rack, for a total of five racks. However, if less than five racks are present in the cluster, then it is still valid to spread out the container replicas among the available racks. For example, if only two racks are available, then one rack will hold three replicas and the other will hold two.