Resize a GCP Filestore down

Filestores deployed using the BASIC_HDD tier (which we do by default) support increasing their size, but not decreasing it. Therefore when we talk about “decreasing the size of a GCP filestore”, we are actually referring to creating a brand new filestore of the desired smaller size, copying all the files across from the larger filestore, and then deleting the larger filestore.

This document details how to proceed with that process.

export CLUSTER_NAME="<cluster-name>"
export HUB_NAME="<hub-name>"

Create a new filestore

Navigate to the terraform/gcp folder in the infrastructure repository and open the relevant projects/<cluster-name>.tfvars file.

Add another filestore definition to the file with config that looks like this:

filestores = {
    "filestore" : {  # This first filestore instance should already be present
        capacity_gb: <larger capacity in GB>
    },
    "filestore_b" : {  # This is the second filestore we are adding
        name_suffix : "b",  # Or something similar
        capacity_gb : <desired, smaller capacity in GB>  # Or remove entirely to use the default of 1GB
    }
}

We add a name_suffix to avoid reusing the name the first filestore was given.

Plan and apply these changes, ensuring only the new filestore is created and nothing else is affected.

terraform plan -var-file=projects/$CLUSTER_NAME.tfvars
terraform apply -var-file=projects/$CLUSTER_NAME.tfvars

Note

If filestore backups are enabled for this cluster, don’t forget to add the name of the new filestore to the cluster’s support values file, following the instructions.

Open a PR and merge these changes so that other engineers cannot accidentally overwrite them.

Migrating the data and switching to the new filestore

See Migrate data across NFS servers for instructions on how to perform these steps.

Decommission the previous filestore

Back in the terraform/gcp folder and <cluster-name>.tfvars file, we can delete the definition of the original filestore.

You also need to temporarily comment out the lifecycle rule in the storage.tf file, otherwise the old filestore is prevented from being destroyed.

Plan and apply these changes, ensuring only the old filestore will be destroyed:

terraform plan -var-file=projects/$CLUSTER_NAME.tfvars
terraform apply -var-file=projects/$CLUSTER_NAME.tfvars

Open and merge a PR with these changes - but DO NOT commit the storage.tf file, you can discard those changes.

Congratulations! You have decreased the size of a GCP Filestore!