Azure Disk CSI Driver Operator - Using Container Storage Interface (CSI) | Storage

Overview of Azure Disk CSI Driver Operator
About CSI
Creating a storage class with storage account type
Performance plus for Azure Disk
User-managed encryption
Machine sets that deploy machines with ultra disks using PVCs
- Creating machines with ultra disks by using machine sets
- Troubleshooting resources for machine sets that enable ultra disks
Additional resources

You can provision and manage Azure Disk storage in OKD by using the Azure Disk Container Storage Interface (CSI) Driver Operator and driver, which provide dynamic volume provisioning and eliminate the need to pre-provision storage.

Overview of Azure Disk CSI Driver Operator

OKD is capable of provisioning persistent volumes (PVs) using the Container Storage Interface (CSI) driver for Microsoft Azure Disk Storage.

Familiarity with persistent storage and configuring CSI volumes is recommended when working with a CSI Operator and driver. For more information about these topics, see "Understanding persistent storage" and "Configuring CSI volumes".

To create CSI-provisioned PVs that mount to Azure Disk storage assets, OKD installs the Azure Disk CSI Driver Operator and the Azure Disk CSI driver by default in the openshift-cluster-csi-drivers namespace.

Azure Disk CSI Driver Operator: The Azure Disk CSI Driver Operator provides a storage class named managed-csi that you can use to create persistent volume claims (PVCs). The Azure Disk 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. You can disable this default storage class if desired (see "Managing the default storage class").
Azure Disk CSI driver: The Azure Disk CSI driver enables you to create and mount Azure Disk PVs.

OKD provides automatic migration for the Azure Disk in-tree volume plugin to its equivalent CSI driver. For more information, see "CSI automatic migration".

Additional resources

About CSI

The Container Storage Interface (CSI) enables storage vendors to deliver plugins through a standard interface without modifying Kubernetes core code, replacing traditional embedded storage drivers.

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

Creating a storage class with storage account type

To provision persistent volumes with specific performance and redundancy characteristics, create a storage class that designates an Azure storage account type corresponding to your SKU tier.

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

When creating a storage class, you can designate the storage account type. This corresponds to your Azure storage account SKU tier. Valid options are Standard_LRS, Premium_LRS, StandardSSD_LRS, UltraSSD_LRS, Premium_ZRS, and StandardSSD_ZRS. For information about finding your Azure SKU tier, see "SKU Types".

Both zone-redundant storage (ZRS) and PremiumV2_LRS have some region limitations. For information about these limitations, see "ZRS limitations" and "Premium_LRS limitations".

Prerequisites

Access to an OKD cluster with administrator rights

Procedure

Create a storage class designating the storage account type using a YAML file similar to the following:
```
$ oc create -f - << EOF
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: <storage-class>
provisioner: disk.csi.azure.com
parameters:
  skuName: <storage-class-account-type>
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
EOF
```
- metadata.name: Specifies the storage class name.
- parameters.skuName: The storage account type. This corresponds to your Azure storage account SKU tier:`Standard_LRS`, Premium_LRS, StandardSSD_LRS, UltraSSD_LRS, Premium_ZRS, StandardSSD_ZRS, PremiumV2_LRS.
  
  For PremiumV2_LRS, specify cachingMode: None in storageclass.parameters.

Ensure that the storage class was created by listing the storage classes:

$ oc get storageclass

Example output

NAME                    PROVISIONER          RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
azurefile-csi           file.csi.azure.com   Delete          Immediate              true                   68m
managed-csi (default)   disk.csi.azure.com   Delete          WaitForFirstConsumer   true                   68m
sc-prem-zrs             disk.csi.azure.com   Delete          WaitForFirstConsumer   true                   4m25s

In this example, sc-prem-zrs is the new storage class with storage account type.

Additional resources

Performance plus for Azure Disk

You can enhance Azure disk performance by enabling performance plus to increase IOPS and throughput limits for certain Azure disk types 513 GiB, and larger.

Overview of performance plus

Performance plus increases Input/Output Operations Per Second (IOPS) and throughput limits for certain Azure disk types 513 GiB, and larger.

The following Azure disk types support performance plus:

Azure Premium solid-state drives (SSD)
Standard SSDs
Standard hard disk drives (HDD)

To see what the increased limits are for IOPS and throughput, consult the columns that begin with Expanded in the tables in "Scalability and performance targets for VM disks".

Additional resources

Scalability and performance targets for VM disks

Limitations for performance plus

To successfully enable performance plus, verify that your disk configuration meets the required type, size, and provisioning criteria before attempting to use this feature.

Performance plus for Azure Disk has the following limitations:

Can be enabled only on Standard HDD, Standard SSD, and Premium SSD managed disks that are 513 GiB or larger.

If you request a smaller value, the disk size is rounded up to 513GiB.
Can be enabled only on new disks. For a workaround, see "Enabling performance plus by snapshot or cloning".

Additional resources

Enabling performance plus by snapshot or cloning

Creating a storage class to use performance plus enhanced disks

To provision Azure disks with enhanced IOPS and throughput, create a storage class with performance plus enabled that automatically applies to persistent volume claims.

Prerequisites

Access to a Microsoft Azure cluster with cluster-admin privileges.
Access to an Azure disk with performance plus enabled.

For information about enabling performance plus on disks, see the "Microsoft Azure storage documentation".

Procedure

Create a storage class using the following example YAML file:
Example storage class YAML file
```
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: <azure-disk-performance-plus-sc>
provisioner: disk.csi.azure.com
parameters:
  skuName: Premium_LRS
  cachingMode: ReadOnly
  enablePerformancePlus: "true"
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
```
- metadata.name: Specifies the name of the storage class.
- provisioner: Specifies the Azure Disk Container Storage Interface (CSI) driver provisioner.
- parameters.skuName: Specifies the Azure disk type SKU. In this example, Premium_LRS for Premium SSD Locally Redundant Storage.
- parameters.enablePerformancePlus: Enables Azure Disk performance plus.
Create a persistent volume claim (PVC) that uses this storage class by using the following example YAML file:
Example PVC YAML file
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: <my-azure-pvc>
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: <azure-disk-performance-plus-sc>
  resources:
    requests:
      storage: 513Gi
```
- metadata.name: Specifies the PVC name.
- spec.storageClassName: References the performance plus storage class.
- spec.resources.requests.storage: Any disk size smaller than 513GiB is automatically rounded up.

Enabling performance plus by snapshot or cloning

To work around the limitation that performance plus applies only to new disks, snapshot or clone an existing volume to provision a new disk with performance plus enabled.

Normally, performance plus can be enabled only on new disks. For a workaround, you can use this procedure.

Prerequisites

Access to a Microsoft Azure cluster with cluster-admin privileges.
Access to an Azure disk with performance plus enabled.
Have created a storage class to use performance plus enhanced Azure disks.

For more information about creating the storage class, see "Creating a storage class to use performance plus enhanced disks".

Procedure

Do one of the following to enable performance plus:
- Create a snapshot of the existing volume that does not have performance plus enabled on it, and then provision a new disk from that snapshot using a storage class with enablePerformancePlus set to "true".
- Clone the persistent volume claim (PVC) using a storage class with enablePerformancePlus set to "true" to create a new disk clone.

Additional resources

Creating a storage class to use performance plus enhanced disks

User-managed encryption

The user-managed encryption feature allows you to provide keys during installation that encrypt OKD node root volumes, and enables all managed storage classes to use these keys to encrypt provisioned storage volumes.

You must specify the custom key in the platform.<cloud_type>.defaultMachinePlatform field in the install-config YAML file.

This features supports the following storage types:

Amazon Web Services (AWS) Elastic Block storage (EBS)

If there is no encrypted key defined in the storage class, only set encrypted: "true" in the storage class. The AWS EBS CSI driver uses the AWS managed alias/aws/ebs, which is created by Amazon EBS automatically in each region by default to encrypt provisioned storage volumes. In addition, the managed storage classes all have the encrypted: "true" setting.

For information about installing AWS EBS with user-managed encryption, see "Optional AWS configuration parameters".

Microsoft Azure Disk storage

If the OS (root) disk is encrypted, and there is no encrypted key defined in the storage class, Azure Disk CSI driver uses the OS disk encryption key by default to encrypt provisioned storage volumes.

For information about installing Azure Disk with user-managed encryption, see "Preparing an Azure Disk Encryption Set".

Google Cloud Platform (GCP) persistent disk (PD) storage

For information about installing GCP PD with user-managed encryption, see "Additional Google Cloud configuration parameters".
IBM Cloud® Virtual Private Cloud (VPC) Block storage

For information about installing with IBM Cloud with user-managed encryption, see "User-managed encryption for IBM Cloud" and "Installing on IBM Cloud".

Additional resources

Preparing an Azure Disk Encryption Set

Machine sets that deploy machines with ultra disks using PVCs

You can create a machine set running on Microsoft Azure that deploys machines with ultra disks. Ultra disks are high-performance storage that are intended for use with the most demanding data workloads.

Both the in-tree plugin and CSI driver support using PVCs to enable ultra disks. You can also deploy machines with ultra disks as data disks without creating a PVC.

Additional resources

Creating machines with ultra disks by using machine sets

You can deploy machines with ultra disks on Microsoft Azure by editing your machine set YAML file.

Prerequisites

Have an existing Microsoft Azure cluster.

Procedure

Copy an existing Azure MachineSet custom resource (CR) and edit it by running the following command:
```
$ oc edit machineset <machine_set_name>
```
where:

<machine_set_name>

Indicates the machine set that you want to provision machines with ultra disks.
Add the following lines in the positions indicated:
```
apiVersion: machine.openshift.io/v1beta1
kind: MachineSet
spec:
  template:
    spec:
      metadata:
        labels:
          disk: ultrassd
      providerSpec:
        value:
          ultraSSDCapability: Enabled
```
where:

spec.template.spec.metadata.labels.disk

Specifies a label to use to select a node that is created by this machine set. The example uses disk.ultrassd for this value.

spec.template.spec.providerSpec.value.ultraSSDCapability

Enables the use of ultra disks.
Create a machine set using the updated configuration by running the following command:
```
$ oc create -f <machine_set_name>.yaml
```
Create a storage class that contains the following YAML definition:
```
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: ultra-disk-sc
parameters:
  cachingMode: None
  diskIopsReadWrite: "2000"
  diskMbpsReadWrite: "320"
  kind: managed
  skuname: UltraSSD_LRS
provisioner: disk.csi.azure.com
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
```
where:

metadata.name

Specifies the name of the storage class. The example uses ultra-disk-sc for this value.

parameters.diskIopsReadWrite

Specifies the number of Input/Output Operations Per Second (IOPS) for the storage class.

parameters.diskMbpsReadWrite

Specifies the throughput in MBps for the storage class.

provisioner

For Microsoft Azure Kubernetes Service (AKS) version 1.21 or later, use disk.csi.azure.com. For earlier versions of AKS, use kubernetes.io/azure-disk.

volumeBindingMode

Optional parameter. Specifies this parameter to wait for the creation of the pod that will use the disk.
Create a persistent volume claim (PVC) to reference the ultra-disk-sc storage class that contains the following YAML definition:
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ultra-disk
spec:
  accessModes:
  - ReadWriteOnce
  storageClassName: ultra-disk-sc
  resources:
    requests:
      storage: 4Gi
```
where:

metadata.name

Specifies the name of the PVC. The example uses ultra-disk for this value.

spec.storageClassName

Specifies the name of the storage class to use. The example uses ultra-disk-sc storage class.

spec.resources.requests.storage

Specifies the size for the storage class. The minimum value is 4Gi.

Create a pod that contains the following YAML definition:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-ultra
spec:
  nodeSelector:
    disk: ultrassd
  containers:
  - name: nginx-ultra
    image: alpine:latest
    command:
      - "sleep"
      - "infinity"
    volumeMounts:
    - mountPath: "/mnt/azure"
      name: volume
  volumes:
    - name: volume
      persistentVolumeClaim:
        claimName: ultra-disk

where:

spec.nodeSelector.disk: Specifies the label of the machine set that enables the use of ultra disks. The example uses disk.ultrassd for this value.
spec.volumes.persistentVolumeClaim.claimName: Specifies the name of the PVC to attach. This pod references the ultra-disk PVC.

Verification

Validate that the machines are created by running the following command:
```
$ oc get machines
```
The machines should be in the Running state.
For a machine that is running and has a node attached, validate the partition by running the following command:
```
$ oc debug node/<node_name> -- chroot /host lsblk
```
In this command, oc debug node/<node_name> starts a debugging shell on the node <node_name> and passes a command with --. The passed command chroot /host provides access to the underlying host OS binaries, and lsblk shows the block devices that are attached to the host OS machine.

Next steps

To use an ultra disk from within a pod, create a workload that uses the mount point. Create a YAML file similar to the following example:

apiVersion: v1
kind: Pod
metadata:
  name: ssd-benchmark1
spec:
  containers:
  - name: ssd-benchmark1
    image: nginx
    ports:
      - containerPort: 80
        name: "http-server"
    volumeMounts:
    - name: lun0p1
      mountPath: "/tmp"
  volumes:
    - name: lun0p1
      hostPath:
        path: /var/lib/lun0p1
        type: DirectoryOrCreate
  nodeSelector:
    disktype: ultrassd

Troubleshooting resources for machine sets that enable ultra disks

You can recover from issues that you might encounter when you enable ultra disks for machine sets. Review fields, such as disk settings, and ensure that the parameters are correctly configured.

Unable to mount a persistent volume claim backed by an ultra disk

If there is an issue mounting a persistent volume claim backed by an ultra disk, the pod becomes stuck in the ContainerCreating state and an alert is triggered.

For example, if the additionalCapabilities.ultraSSDEnabled parameter is not set on the machine that backs the node that hosts the pod, the following error message appears:

StorageAccountType UltraSSD_LRS can be used only when additionalCapabilities.ultraSSDEnabled is set.

To resolve this issue, describe the pod by running the following command:
```
$ oc -n <stuck_pod_namespace> describe pod <stuck_pod_name>
```