Create a VHD blob using Azure Go SDK

There is no good tutorials on how to create a VHD blob that can serve as VM’s Data Disk on Azure. So I write some note on it, based on my recent Kubernetes PR 30091 as part of the effort to support Azure Data Disk dynamic provisioning.

This work uses Azure’s ASM and ARM modes: ARM mode to extract Storage Account name, key, Sku tier, location; ASM mode to list, create, and delete Azure Page Blob.

When an inquiry comes to find an Azure Storage account that has a Sku tier Standard_LRS and location eastus, all Storage accounts are listed. This is accomplished by getStorageAccounts(), which calls ListByResourceGroup() in Azure Go SDK. Each account returns its name, location, and Sku tier. Once a matching account is identified, the access key is retrieved via getStorageAccesskey(), which calls Azure SDK’s ListKeys().

Creating a VHD blob must use the classic Storage API that require account name and access key. createVhdBlob takes the account name and key and a creates a VHD blob in the account’s vhds Container. This uses Azure SDK’s PutPageBlob() method. Once the Page Blob is created, a VHD footer must be created at the end of the blob. This is currently accomplished in my forked go-vhd that is also upstreamed. The VHD footer appends to the blob by calling SDK’s PutPage() method.

Now the Page Blob is created, it can be used as Azure VM’s Data Disk.

A prototype data disk dynamic provisioning on Kubernetes can be found at my branch . A quick demo is as the following.

First create a Storage Class

kind: StorageClass
apiVersion: extensions/v1beta1
metadata:
 name: slow
provisioner: kubernetes.io/azure-disk
parameters:
 skuName: Standard_LRS
 location: eastus

Then create a Persistent Volume Claim like this

Once created, it should be like

# _output/bin/kubectl describe pvc
Name: claim1
Namespace: default
Status: Bound
Volume: pvc-37ff3ec3-5ceb-11e6-88a3-000d3a12e034
Labels: <none>
Capacity: 3Gi
Access Modes: RWO
No events.

Create a Pod that uses the claim:

apiVersion: v1
kind: ReplicationController
metadata:
name: nfs-server
spec:
    replicas: 1
    selector:
       role: nfs-server
    template:
       metadata:
         labels:
           role: nfs-server
    spec:
       containers:
       - name: nfs-server
         image: nginx
       volumeMounts:
         - mountPath: /exports
           name: mypvc
       volumes:
          - name: mypvc
            persistentVolumeClaim:
               claimName: claim1

 

The Pod should run with the dynamically provisioned Data Disk.