# Placement groups for EC2 instances in AWS PCS
<a name="working-with_networking_placement-groups"></a>

 You can use a **placement group** to influence the placement of EC2 instances to suit the needs of the workload that runs on them.

**Placement group types**
+  **Cluster** – Packs instances close together in an Availability Zone to optimize for low-latency communication. 
+  **Partition** – Spreads instances across logical partitions to help maximize resilience.
+  **Spread** – Strictly enforces that a small number of instances launch on distinct hardware, which can also help with resiliency.

For more information, see [Placement groups for your Amazon EC2 instances](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html) in the *Amazon Elastic Compute Cloud User Guide*.

We recommended you include a **cluster** placement group when you configure an AWS PCS compute node group to use Elastic Fabric Adapter (EFA).

**To create a cluster placement group that works with EFA**

1. Create a placement group with the type **cluster** for the compute node group.
   + Use the following AWS CLI command:

     ```
     aws ec2 create-placement-group --strategy cluster --group-name PLACEMENT-GROUP-NAME
     ```
   + You can also use a CloudFormation template to create a placement group. For more information, see [Working with CloudFormation templates](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-guide.html) in the *AWS CloudFormation User Guide*. Download the template from the following URL and upload it into the [CloudFormation console](https://console.aws.amazon.com/cloudformation).

     ```
     https://aws-hpc-recipes.s3.amazonaws.com/main/recipes/pcs/enable_efa/assets/efa-placement-group.yaml
     ```

1.  Include the placement group in the EC2 launch template for the AWS PCS compute node group.