Use Azure Container Storage Preview with Ephemeral Disk

Article
04/01/2024

Azure Container Storage is a cloud-based volume management, deployment, and orchestration service built natively for containers. This article shows you how to configure Azure Container Storage to use Ephemeral Disk as back-end storage for your Kubernetes workloads. At the end, you'll have a pod that's using either local NVMe or temp SSD as its storage.

Important

Local disks are ephemeral, meaning that they're created on the local virtual machine (VM) storage and not saved to an Azure storage service. Data will be lost on these disks if you stop/deallocate your VM. You can only create Kubernetes generic ephemeral volumes from an Ephemeral Disk storage pool. If you want to create a persistent volume, you have to enable replication for your storage pool.

Prerequisites

If you don't have an Azure subscription, create a free account before you begin.
This article requires the latest version (2.35.0 or later) of the Azure CLI. See How to install the Azure CLI. If you're using the Bash environment in Azure Cloud Shell, the latest version is already installed. If you plan to run the commands locally instead of in Azure Cloud Shell, be sure to run them with administrative privileges. For more information, see Get started with Azure Cloud Shell.
You'll need the Kubernetes command-line client, kubectl. It's already installed if you're using Azure Cloud Shell, or you can install it locally by running the az aks install-cli command.

If you haven't already installed Azure Container Storage, follow the instructions in Install Azure Container Storage.

Note

To use Azure Container Storage with Ephemeral Disk, your AKS cluster should have a node pool of at least three storage optimized VMs such as standard_l8s_v3. We recommend that each VM have a minimum of four virtual CPUs (vCPUs).

Regional availability

Azure Container Storage is only available for a subset of Azure regions:

(Africa) South Africa North
(Asia Pacific) Australia East
(Asia Pacific) East Asia
(Asia Pacific) Japan East
(Asia Pacific) Korea Central
(Asia Pacific) Southeast Asia
(Asia Pacific) Central India
(Europe) France Central
(Europe) North Europe
(Europe) West Europe
(Europe) UK South
(Europe) Sweden Central
(Europe) Switzerland North
(Middle East) UAE North
(North America) East US
(North America) East US 2
(North America) West US
(North America) West US 2
(North America) West US 3
(North America) Central US
(North America) North Central US
(North America) South Central US
(North America) West Central US
(North America) Canada Central
(North America) Canada East
(South America) Brazil South

Create a storage pool

First, create a storage pool, which is a logical grouping of storage for your Kubernetes cluster, by defining it in a YAML manifest file.

If you enabled Azure Container Storage using az aks create or az aks update commands, you might already have a storage pool. Use kubectl get sp -n acstor to get the list of storage pools. If you have a storage pool already available that you want to use, you can skip this section and proceed to Display the available storage classes.

You have three options to create a storage pool that uses Ephemeral Disk:

Create storage pool with local NVMe
Create storage pool with temp SSD
Create storage pool with local NVMe and replication

Create a storage pool with NVMe

Follow these steps to create a storage pool using local NVMe.

Use your favorite text editor to create a YAML manifest file such as code acstor-storagepool.yaml.

Paste in the following code and save the file. The storage pool name value can be whatever you want.

apiVersion: containerstorage.azure.com/v1
kind: StoragePool
metadata:
  name: ephemeraldisk
  namespace: acstor
spec:
  poolType:
    ephemeralDisk: {}

Apply the YAML manifest file to create the storage pool.
```
kubectl apply -f acstor-storagepool.yaml 
```
When storage pool creation is complete, you'll see a message like:
```
storagepool.containerstorage.azure.com/ephemeraldisk created
```
You can also run this command to check the status of the storage pool. Replace <storage-pool-name> with your storage pool name value. For this example, the value would be ephemeraldisk.
```
kubectl describe sp <storage-pool-name> -n acstor
```

When the storage pool is created, Azure Container Storage will create a storage class on your behalf, using the naming convention acstor-<storage-pool-name>.

Create a storage pool with temp SSD

Follow these steps to create a storage pool using temp SSD.

Use your favorite text editor to create a YAML manifest file such as code acstor-storagepool.yaml.

Paste in the following code and save the file. The storage pool name value can be whatever you want.

apiVersion: containerstorage.azure.com/v1
kind: StoragePool
metadata:
  name: ephemeraldisk
  namespace: acstor
spec:
  poolType:
    ephemeralDisk:
      diskType: temp

Apply the YAML manifest file to create the storage pool.
```
kubectl apply -f acstor-storagepool.yaml 
```
When storage pool creation is complete, you'll see a message like:
```
storagepool.containerstorage.azure.com/ephemeraldisk created
```
You can also run this command to check the status of the storage pool. Replace <storage-pool-name> with your storage pool name value. For this example, the value would be ephemeraldisk.
```
kubectl describe sp <storage-pool-name> -n acstor
```

When the storage pool is created, Azure Container Storage will create a storage class on your behalf, using the naming convention acstor-<storage-pool-name>.

Display the available storage classes

When the storage pool is ready to use, you must select a storage class to define how storage is dynamically created when creating persistent volume claims and deploying persistent volumes.

Run kubectl get sc to display the available storage classes. You should see a storage class called acstor-<storage-pool-name>.

Important

Don't use the storage class that's marked internal. It's an internal storage class that's needed for Azure Container Storage to work.

Deploy a pod with a generic ephemeral volume

Create a pod using Fio (Flexible I/O Tester) for benchmarking and workload simulation, that uses a generic ephemeral volume.

Use your favorite text editor to create a YAML manifest file such as code acstor-pod.yaml.

Paste in the following code and save the file.

kind: Pod
apiVersion: v1
metadata:
  name: fiopod
spec:
  nodeSelector:
    acstor.azure.com/io-engine: acstor
  containers:
    - name: fio
      image: nixery.dev/shell/fio
      args:
        - sleep
        - "1000000"
      volumeMounts:
        - mountPath: "/volume"
          name: ephemeralvolume
  volumes:
    - name: ephemeralvolume
      ephemeral:
        volumeClaimTemplate:
          metadata:
            labels:
              type: my-ephemeral-volume
          spec:
            accessModes: [ "ReadWriteOnce" ]
            storageClassName: "acstor-ephemeraldisk-nvme" # replace with the name of your storage class if different
            resources:
              requests:
                storage: 1Gi

Apply the YAML manifest file to deploy the pod.
```
kubectl apply -f acstor-pod.yaml
```
You should see output similar to the following:
```
pod/fiopod created
```
Check that the pod is running and that the ephemeral volume claim has been bound successfully to the pod:
```
kubectl describe pod fiopod
kubectl describe pvc fiopod-ephemeralvolume
```

Check fio testing to see its current status:

kubectl exec -it fiopod -- fio --name=benchtest --size=800m --filename=/volume/test --direct=1 --rw=randrw --ioengine=libaio --bs=4k --iodepth=16 --numjobs=8 --time_based --runtime=60

You've now deployed a pod that's using Ephemeral Disk as its storage, and you can use it for your Kubernetes workloads.

Expand a storage pool

You can expand storage pools backed by local NVMe or temp SSD to scale up quickly and without downtime. Shrinking storage pools isn't currently supported.

Because a storage pool backed by Ephemeral Disk uses local storage resources on the AKS cluster nodes (VMs), expanding the storage pool requires adding another node to the cluster. Follow these instructions to expand the storage pool.

Run the following command to add a node to the AKS cluster. Replace <cluster-name>, <nodepool name>, and <resource-group-name> with your own values. To get the name of your node pool, run kubectl get nodes.
```
az aks nodepool add --cluster-name <cluster name> --name <nodepool name> --resource-group <resource group> --node-vm-size Standard_L8s_v3 --node-count 1 --labels acstor.azure.com/io-engine=acstor
```
Run kubectl get nodes and you'll see that a node has been added to the cluster.
Run kubectl get sp -A and you should see that the capacity of the storage pool has increased.

Delete a storage pool

If you want to delete a storage pool, run the following command. Replace <storage-pool-name> with the storage pool name.

kubectl delete sp -n acstor <storage-pool-name>

Optional: Create storage pool with volume replication (NVMe only)

Applications that use local NVMe can leverage storage replication for improved resiliency. Replication isn't currently supported for temp SSD.

Azure Container Storage currently supports three-replica and five-replica configurations. If you specify three replicas, you must have at least three nodes in your AKS cluster. If you specify five replicas, you must have at least five nodes.

Follow these steps to create a storage pool using local NVMe with replication.

Note

Because Ephemeral Disk storage pools consume all the available NVMe disks, you must delete any existing Ephemeral Disk local NVMe storage pools before creating a new storage pool with replication.

Use your favorite text editor to create a YAML manifest file such as code acstor-storagepool.yaml.

Paste in the following code and save the file. The storage pool name value can be whatever you want. Set replicas to 3 or 5.

apiVersion: containerstorage.azure.com/v1
kind: StoragePool
metadata:
  name: nvme
  namespace: acstor
spec:
  poolType:
    ephemeralDisk:
      diskType: nvme
      replicas: 3

Apply the YAML manifest file to create the storage pool.
```
kubectl apply -f acstor-storagepool.yaml 
```
When storage pool creation is complete, you'll see a message like:
```
storagepool.containerstorage.azure.com/nvme created
```
You can also run this command to check the status of the storage pool. Replace <storage-pool-name> with your storage pool name value. For this example, the value would be nvme.
```
kubectl describe sp <storage-pool-name> -n acstor
```

When the storage pool is created, Azure Container Storage will create a storage class on your behalf, using the naming convention acstor-<storage-pool-name>. Now you can display the available storage classes and create a persistent volume claim.

Create a persistent volume claim

A persistent volume claim (PVC) is used to automatically provision storage based on a storage class. Follow these steps to create a PVC using the new storage class.

Use your favorite text editor to create a YAML manifest file such as code acstor-pvc.yaml.

Paste in the following code and save the file. The PVC name value can be whatever you want.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ephemeralpvc
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: acstor-ephemeraldisk-nvme # replace with the name of your storage class if different
  resources:
    requests:
      storage: 100Gi

Apply the YAML manifest file to create the PVC.
```
kubectl apply -f acstor-pvc.yaml
```
You should see output similar to:
```
persistentvolumeclaim/ephemeralpvc created
```
You can verify the status of the PVC by running the following command:
```
kubectl describe pvc ephemeralpvc
```

Once the PVC is created, it's ready for use by a pod.

Deploy a pod and attach a persistent volume

Create a pod using Fio (Flexible I/O Tester) for benchmarking and workload simulation, and specify a mount path for the persistent volume. For claimName, use the name value that you used when creating the persistent volume claim.

Use your favorite text editor to create a YAML manifest file such as code acstor-pod.yaml.