h. Update your cluster

We have sucessfully built your cluster and ran your first MPI job.

Let’s say you want to change your instance type to a different instance type in your compute fleet for example c4.large . In this lab, we will learn how to update your cluster with new instance type.

Go back to your AWS Cloud9 environment, and stop the cluster

pcluster list
pcluster stop hpclab-yourname

Edit your original config file and change instance_type = c4.large

vi my-cluster-config.ini 
[compute_resource default]
instance_type = c4.large
min_count = 0
max_count = 8

Then run a pcluster update command

pcluster update hpclab-yourname -c my-cluster-config.ini

Pay attention to the old value and new value fields. You will see a new instance type under new value field. The output will be similar to this.

ParallelCluster Update

Start your cluster again after update process is completed.

pcluster start hpclab-yourname

You can now login to your cluster and run your helloworld job again

you can see that the cluster compute node has changed to c4.large

[ec2-user@ip-172-31-39-157 ~]$ sinfo
PARTITION AVAIL  TIMELIMIT  NODES  STATE NODELIST 
compute*     up   infinite      8  idle~ compute-dy-c4large-[1-8] 

Now you have a better understanding on how AWS ParallelCluster operates. For more information, see the Configuration section of the AWS ParallelCluster User Guide.