Placement groups and instance launch issues - Amazon ParallelCluster
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Placement groups and instance launch issues

To get the lowest inter-node latency, use a placement group. A placement group ensures that your instances are on the same networking backbone. If there aren't enough instances available when a request is made, an InsufficientInstanceCapacity error is returned. To reduce the possibility of receiving this error when using cluster placement groups, set the SlurmQueues / Networking / PlacementGroup / Enabled parameter to false.

For additional control over capacity access, consider launching instances with ODCR (On-Demand Capacity Reservations).

For more information, see Troubleshooting instance launch issues and Placement groups roles and limitations in the Amazon EC2 User Guide for Linux Instances.