Overview

OKD is capable of provisioning persistent volumes (PVs) using the Container Storage Interface (CSI) driver for AWS Elastic File Service (EFS).

AWS EFS Driver Operator is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

Familiarity with persistent storage and configuring CSI volumes is recommended when working with a CSI Operator and driver.

After installing the AWS EFS CSI Driver Operator, OKD installs the AWS EFS CSI Operator and the AWS EFS CSI driver by default in the openshift-cluster-csi-drivers namespace. This allows the AWS EFS CSI Driver Operator to create CSI-provisioned PVs that mount to AWS EFS assets.

  • The AWS EFS CSI Driver Operator, after being installed, does not create a storage class by default to use to create persistent volume claims (PVCs). However, you can manually create the AWS EFS StorageClass. The AWS EFS CSI Driver Operator supports dynamic volume provisioning by allowing storage volumes to be created on-demand, eliminating the need for cluster administrators to pre-provision storage.

  • The AWS EFS CSI driver enables you to create and mount AWS EFS PVs. The AWS EFS CSI driver must be manually installed.

AWS EFS only supports regional volumes, not zonal volumes.

About CSI

Storage vendors have traditionally provided storage drivers as part of Kubernetes. With the implementation of the Container Storage Interface (CSI), third-party providers can instead deliver storage plug-ins using a standard interface without ever having to change the core Kubernetes code.

CSI Operators give OKD users storage options, such as volume snapshots, that are not possible with in-tree volume plug-ins.

Installing the AWS EFS CSI Driver Operator

The AWS EFS CSI Driver Operator is not installed in OKD by default. Use the following procedure to install and configure the AWS EFS CSI Driver Operator in your cluster.

Prerequisites
  • Access to the OKD web console.

Procedure

To install the AWS EFS CSI Driver Operator from the web console:

  1. Log in to the web console.

  2. Install the AWS EFS CSI Operator:

    1. Click OperatorsOperatorHub.

    2. Locate the AWS EFS CSI Operator by typing AWS EFS CSI in the filter box.

    3. Click the AWS EFS CSI Driver Operator button.

      Be sure to select the AWS EFS CSI Driver Operator and not the AWS EFS Operator. The AWS EFS Operator is a community Operator and is not supported by Red Hat.

    4. On the AWS EFS CSI Driver Operator page, click Install.

    5. On the Install Operator page, ensure that:

      • All namespaces on the cluster (default) is selected.

      • Installed Namespace is set to openshift-cluster-csi-drivers.

    6. Click Install.

      After the installation finishes, the AWS EFS CSI Operator is listed in the Installed Operators section of the web console.

  3. Install the AWS EFS CSI Driver:

    1. Click administrationCustomResourceDefinitionsClusterCSIDriver.

    2. On the Instances tab, click Create ClusterCSIDriver.

    3. Use the following YAML file:

      apiVersion: operator.openshift.io/v1
      kind: ClusterCSIDriver
      metadata:
          name: efs.csi.aws.com
      spec:
        managementState: Managed
    4. Click Create.

    5. Wait for the following Conditions to change to a "true" status:

      • AWSEFSDriverCredentialsRequestControllerAvailable

      • AWSEFSDriverNodeServiceControllerAvailable

      • AWSEFSDriverControllerServiceControllerAvailable

Creating the AWS EFS storage class

Storage classes are used to differentiate and delineate storage levels and usages. By defining a storage class, users can obtain dynamically provisioned persistent volumes.

The AWS EFS CSI Driver Operator, after being installed, does not create a storage class by default. However, you can manually create the AWS EFS StorageClass.

Procedure
  1. In the OKD console, click StorageStorage Classes.

  2. On the StorageClasses overview page, click Create Storage Class.

  3. On the StorageClasses create page, enter values as desired:

    1. Enter a name to reference the storage class.

    2. Enter an optional description.

    3. Select the reclaim policy.

    4. Select efs.csi.aws.com from the Provisioner drop-down list.

    5. Enter additional parameters for the storage class as desired.

  4. Click Create.

Creating and configuring access to EFS volumes in AWS

This procedure explains how to create and configure EFS volumes in AWS so that you can use them in OKD.

Prerequisites
  • AWS account credentials

Procedure

To create and configure access to an EFS volume in AWS:

  1. On the AWS console, open https://console.aws.amazon.com/efs.

  2. Click Create file system:

    • Enter a name for the file system.

    • For Virtual Private Cloud (VPC), select your OKD’s' virtual private cloud (VPC).

    • Accept default settings for all other selections.

  3. Wait for the volume and mount targets to finish being fully created:

    1. Go to https://console.aws.amazon.com/efs#/file-systems.

    2. Click your volume, and on the Network tab wait for all mount targets to become available (~1-2 minutes).

  4. On the Network tab, copy the Security Group ID (you will need this in the next step).

  5. Go to https://console.aws.amazon.com/ec2/v2/home#SecurityGroups, and find the Security Group used by the EFS volume.

  6. On the Inbound rules tab, click Edit inbound rules, and then add a new rule with the following settings to allow OKD nodes to access EFS volumes :

    • Type: NFS

    • Protocol: TCP

    • Port range: 2049

    • Source: Custom/IP address range of your nodes (for example: “10.0.0.0/16”)

      This step allows OKD to use NFS ports from the cluster.

  7. Save the rule.

Dynamic provisioning for AWS EFS

The AWS EFS CSI Driver supports a different form of dynamic provisioning than other CSI drivers. It provisions new PVs as subdirectories of a pre-existing EFS volume. The PVs are independent of each other. However, they all share the same EFS volume. When the volume is deleted, all PVs provisioned out of it are deleted too. The EFS CSI driver creates an AWS Access Point for each such subdirectory. Due to AWS AccessPoint limits, you can only dynamically provision 120 PVs from a single StorageClass/EFS volume.

Note that PVC.spec.resources is not enforced by EFS.

In the example below, you request 5 GiB of space. However, the created PV is limitless and can store any amount of data (like petabytes). A broken application, or even a rogue application, can cause significant expenses when it stores too much data on the volume.

Using monitoring of EFS volume sizes in AWS is strongly recommended.

Procedure

To enable dynamic provisioning:

  1. Create a StorageClass as follows:

    kind: StorageClass
    apiVersion: storage.k8s.io/v1
    metadata:
      name: efs-sc
    provisioner: efs.csi.aws.com
    parameters:
      provisioningMode: efs-ap (1)
      fileSystemId: fs-a5324911 (2)
      directoryPerms: "700" (3)
      gidRangeStart: "1000" (4)
      gidRangeEnd: "2000" (4)
      basePath: "/dynamic_provisioning" (5)
    1 provisioningMode must be efs-ap to enable dynamic provisioning.
    2 fileSystemId must be the ID of the EFS volume created manually above.
    3 directoryPerms is the default permission of the root directory of the volume. In this case, the volume is accessible only by the owner.
    4 gidRangeStart and gidRangeEnd set the range of POSIX Group IDs (GIDs) that are used to set the GID of the AWS access point. If not specified, the default range is 50000-7000000. Each provisioned volume, and thus AWS access point, is assigned a unique GID from this range.
    5 basePath is the directory on the EFS volume that is used to create dynamically provisioned volumes. In this case, a PV is provisioned as “/dynamic_provisioning/<random uuid>” on the EFS volume. Only the subdirectory is mounted to pods that use the PV.

    A cluster admin can create several StorageClasses, each using a different EFS volume.

  2. Create a PVC (or StatefulSet or Template) as usual, referring to the StorageClass created above.

    apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      name: test
    spec:
      storageClassName: efs-sc
      accessModes:
        - ReadWriteMany
      resources:
        requests:
          storage: 5Gi

If you have problems setting up dynamic provisioning, see AWS EFS troubleshooting.

Creating static PVs with AWS EFS

It is possible to use an AWS EFS volume as a single PV without any dynamic provisioning. The whole volume is mounted to pods.

Procedure
  • Create the PV using the following YAML file:

    apiVersion: v1
    kind: PersistentVolume
    metadata:
      name: efs-pv
    spec:
      capacity: (1)
        storage: 5Gi
      volumeMode: Filesystem
      accessModes:
        - ReadWriteMany
        - ReadWriteOnce
      persistentVolumeReclaimPolicy: Retain
      csi:
        driver: efs.csi.aws.com
        volumeHandle: fs-ae66151a (2)
        volumeAttributes:
            encryptInTransit: false (3)
    1 spec.capacity does not have any meaning and is ignored by the CSI driver. It is used only when binding to a PVC. Applications can store any amount of data to the volume.
    2 volumeHandle must be the same ID as the EFS volume you created in AWS. If you are providing your own access point, volumeHandle should be <EFS volume ID>::<access point ID>. For example: fs-6e633ada::fsap-081a1d293f0004630.
    3 If desired, you can disable encryption in transit. Encryption is enabled by default.

If you have problems setting up static PVs, see AWS EFS troubleshooting.

AWS EFS security

The following information is important for AWS EFS security.

When using access points, for example, by using dynamic provisioning as described earlier, Amazon automatically replaces GIDs on files with the GID of the access point. In addition, EFS considers the user ID, group ID, and secondary group IDs of the access point when evaluating file system permissions. EFS ignores the NFS client’s IDs. For more information about access points, see https://docs.aws.amazon.com/efs/latest/ug/efs-access-points.html.

As a consequence, EFS volumes silently ignore FSGroup; OKD is not able to replace the GIDs of files on the volume with FSGroup. Any pod that can access a mounted EFS access point can access any file on it.

Unrelated to this, encryption in transit is enabled by default. For more information, see https://docs.aws.amazon.com/efs/latest/ug/encryption-in-transit.html.

AWS EFS troubleshooting

The following information provides guidance on how to troubleshoot issues with AWS EFS:

  • The AWS EFS Operator and CSI driver run in namespace openshift-cluster-csi-drivers.

  • To initiate gathering of logs of the AWS EFS Operator and CSI driver, run the following command:

    $ oc adm must-gather
    [must-gather      ] OUT Using must-gather plugin-in image: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:125f183d13601537ff15b3239df95d47f0a604da2847b561151fedd699f5e3a5
    [must-gather      ] OUT namespace/openshift-must-gather-xm4wq created
    [must-gather      ] OUT clusterrolebinding.rbac.authorization.k8s.io/must-gather-2bd8x created
    [must-gather      ] OUT pod for plug-in image quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:125f183d13601537ff15b3239df95d47f0a604da2847b561151fedd699f5e3a5 created
  • To show AWS EFS Operator errors, view the ClusterCSIDriver status:

    $ oc get clustercsidriver efs.csi.aws.com -o yaml
  • If a volume cannot be mounted to a pod (as shown in the output of the following command):

    $ oc describe pod
    ...
      Type     Reason       Age    From               Message
      ----     ------       ----   ----               -------
      Normal   Scheduled    2m13s  default-scheduler  Successfully assigned default/efs-app to ip-10-0-135-94.ec2.internal
      Warning  FailedMount  13s    kubelet            MountVolume.SetUp failed for volume "pvc-d7c097e6-67ec-4fae-b968-7e7056796449" : rpc error: code = DeadlineExceeded desc = context deadline exceeded (1)
      Warning  FailedMount  10s    kubelet            Unable to attach or mount volumes: unmounted volumes=[persistent-storage], unattached volumes=[persistent-storage kube-api-access-9j477]: timed out waiting for the condition
    1 Warning message indicating volume not mounted.

    This error is frequently caused by AWS dropping packets between an OKD node and AWS EFS.

    Check that the following are correct (see Creating and configuring access to EFS volumes in AWS):

    • AWS firewall and Security Groups

    • Networking: port number and IP addresses

Uninstalling the AWS EFS CSI Driver Operator

All EFS PVs are inaccessible after uninstalling the AWS EFS CSI Driver Operator.

Prerequisites
  • Access to the OKD web console.

Procedure

To uninstall the AWS EFS CSI Driver Operator from the web console:

  1. Log in to the web console.

  2. Stop all applications that use AWS EFS PVs.

  3. Delete all AWS EFS PVs:

    1. Click StoragePersistentVolumeClaims.

    2. Select each PVC that is in use by the AWS EFS CSI Driver Operator, click the drop-down menu on the far right of the PVC, and then click Delete PersistentVolumeClaims.

  4. Uninstall the AWS EFS CSI Driver:

    Before you can uninstall the Operator, you must remove the CSI driver first.

    1. Click administrationCustomResourceDefinitionsClusterCSIDriver.

    2. On the Instances tab, for efs.csi.aws.com, on the far left side, click the drop-down menu, and then click Delete ClusterCSIDriver.

    3. When prompted, click Delete.

  5. Uninstall the AWS EFS CSI Operator:

    1. Click OperatorsInstalled Operators.

    2. On the Installed Operators page, scroll or type AWS EFS CSI into the Search by name box to find the Operator, and then click it.

    3. On the upper, right of the Installed Operators > Operator details page, click ActionsUninstall Operator.

    4. When prompted on the Uninstall Operator window, click the Uninstall button to remove the Operator from the namespace. Any applications deployed by the Operator on the cluster need to be cleaned up manually.

      After uninstalling, the AWS EFS CSI Driver Operator is no longer listed in the Installed Operators section of the web console.

Before you can destroy a cluster (openshift-install destroy cluster), you must delete the EFS volume in AWS. An OKD cluster cannot be destroyed when there is an EFS volume that uses the cluster’s VPC. Amazon does not allow deletion of such a VPC.

Additional resources