placementGroup

The Amazon EC2 placement group to associate with your compute resources. If you intend to submit multi-node parallel jobs to your compute environment, you should consider creating a cluster placement group and associate it with your compute resources. This keeps your multi-node parallel job on a logical grouping of instances within a single Availability Zone with high network flow potential. For more information, see Placement groups in the Amazon EC2 User Guide for Linux Instances.

This parameter isn't applicable to jobs that are running on Fargate resources. Don't specify it.