sharedisk

Shared disk

Feature Status: GA

Azure shared disks is a new feature for Azure managed disks that enables attaching an Azure managed disk to multiple virtual machines (VMs) simultaneously. Attaching a managed disk to multiple VMs allows you to either deploy new or migrate existing clustered applications to Azure.

Note

Only raw block device(volumeMode: Block) is supported on shared disk feature, Kubernetes application should manage coordination and control of writes, reads, locks, caches, mounts, fencing on the shared disk which is exposed as raw block device. Multi-node read write is not supported by common file systems (e.g. ext4, xfs), it's only supported by cluster file systems.

Example

1. Create Storage Class and PVC

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: managed-csi
provisioner: disk.csi.azure.com
parameters:
  skuName: Premium_LRS
  maxShares: "2"
  cachingMode: None  # ReadOnly cache is not available for premium SSD with maxShares>1
reclaimPolicy: Delete
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc-azuredisk
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 256Gi  # minimum size of shared disk is 256GB (P15)
  volumeMode: Block
  storageClassName: managed-csi

2. Create a deployment with 2 replicas and specify volumeDevices, devicePath in Spec

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: deployment-azuredisk
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
      name: deployment-azuredisk
    spec:
      containers:
        - name: deployment-azuredisk
          image: mcr.microsoft.com/oss/nginx/nginx:1.17.3-alpine
          volumeDevices:
            - name: azuredisk
              devicePath: /dev/sdx
      volumes:
        - name: azuredisk
          persistentVolumeClaim:
            claimName: pvc-azuredisk

3. Check block device in pod

# kubectl exec -it deployment-sharedisk-7454978bc6-xh7jp bash
root@deployment-sharedisk-7454978bc6-xh7jp:/# dd if=/dev/zero of=/dev/sdx bs=1024k count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB, 100 MiB) copied, 0.0502999 s, 2.1 GB/s