Spread Placement Group Rules and Limitations
The following rules (guidelines) apply to the Spread Placement Group
- The most running instances that can be supported by a rack spread placement group are seven. A Region with three Availability Zones, for instance, allows you to run a total of 21 instances in the group, with seven instances in each Availability Zone. Eighth instances cannot launch if they are started in the same Availability Zone and spread placement group. We suggest using multiple spread deployment groups if you want more than seven instances in a given Availability Zone. Using several spread placement groups helps ensure the spread for each group but not guaranteeing the spread of instances between groups, hence reducing the impact of specific failure classes.
- Dedicated Instances do not allow spread placement groups. The Spread placement strategy is only available for EC2 instances that are homogeneous in terms of their instance type and network performance.
- Only AWS Outposts allow host-level spread placement groups for placement groups. With host-level spread placement groups, there are no limitations on the number of running instances.
- Capacity reservations cannot be used to reserve space in a spread placement group.
- Space in a spread placement group is not reserved by reservations for capacity.
- The Spread placement strategy does not support integration with Elastic Load Balancers (ELBs).
- The Spread placement strategy assumes that all instances in the Auto Scaling group have the same network performance characteristics, so it may not be suitable for instances with varying network performance needs.
Placement Group Rules and Limitations
Pre-requisite: EC2
Placement groups are a mechanism used in Amazon Elastic Compute Cloud (EC2) for controlling the placement of instances in a cluster. They have some rules and limitations that you need to be aware of when using them.
Here are some of the rules and limitations of Placement Groups:
- General Rules and Limitations
- Cluster Placement Group Rules and Limitations
- Partition Placement Group Rules and Limitations
- Spread Placement Group Rules and Limitations