# Elastic Fabric Adapter
<a name="efa"></a>

An Elastic Fabric Adapter (EFA) is a network device to accelerate High Performance Computing (HPC) applications. AWS Batch supports applications that use EFA if the following conditions are met.
+ For a list of instance types that support EFAs, see [Supported instance types](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/efa.html#efa-instance-types) in the *Amazon EC2 User Guide*.
**Tip**  
To see a list of instance types that support EFAs in an AWS Region, run the following command. Then, cross reference the list that's returned with the list of available instance types in the AWS Batch console.  

  ```
  $ aws ec2 describe-instance-types  --region us-east-1  --filters Name=network-info.efa-supported,Values=true  --query "InstanceTypes[*].[InstanceType]"  --output text | sort
  ```
+ For a list of operating systems that support EFA, see [Supported operating systems](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/efa.html#efa-os).
+ The AMI has the EFA driver loaded.
+ The security group for the EFA must allows all inbound and outbound traffic to and from the security group itself.
+ All instances that use an EFA must be in the same cluster placement group.
+ The job definition must include a `devices` member with `hostPath` set to `/dev/infiniband/uverbs0` to allow the EFA device to be passed through to the container. If `containerPath` is specified, it must also be set to `/dev/infiniband/uverbs0`. If `permissions` is set it must be set to `READ` \$1 `WRITE` \$1 `MKNOD`.

  The location of the [LinuxParameters](https://docs.aws.amazon.com/batch/latest/APIReference/API_LinuxParameters.html) members are different for multi-node parallel jobs and single-node container jobs. The following examples show the differences, but are missing required values.  
**Example for multi-node parallel job**  

  ```
  {
    "jobDefinitionName": "EFA-MNP-JobDef",
    "type": "multinode",
    "nodeProperties": {
      ...
      "nodeRangeProperties": [
        {
          ...
          "container": {
            ...
            "linuxParameters": {
              "devices": [
                {
                  "hostPath": "/dev/infiniband/uverbs0",
                  "containerPath": "/dev/infiniband/uverbs0",
                  "permissions": [
                      "READ", "WRITE", "MKNOD"
                  ]
                },
              ],
            },
          },
        },
      ],
    },
  }
  ```  
**Example for single-node container job**  

  ```
  {
    "jobDefinitionName": "EFA-Container-JobDef",
    "type": "container",
    ...
    "containerProperties": {
      ...
      "linuxParameters": {
        "devices": [
          {
            "hostPath": "/dev/infiniband/uverbs0",
          },
        ],
      },
    },
  }
  ```

For more information about EFA, see [Elastic Fabric Adapter](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/efa.html) in *Amazon EC2 User Guide*.