Azure Blob Storage CSI driver mountpoint on AKS pod does not have enough capacity as expected

Question

I followed this documentation to enable the CSI driver for Azure Blob Storage on my AKS cluster. After the installation, I deployed a sample Nginx pod associated with a PVC provisioned by the above driver, but the mount point only shows 1000M, which is not equal to the request (100GiB).

Here's my sample manifest file:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: statefulset-blob
  labels:
    app: nginx
spec:
  serviceName: statefulset-blob
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx
    spec:
      nodeSelector:
        "kubernetes.io/os": linux
      containers:
        - name: statefulset-blob
          image: nginx:latest
          volumeMounts:
            - name: persistent-storage
              mountPath: /mnt/blob
  updateStrategy:
    type: RollingUpdate
  selector:
    matchLabels:
      app: nginx
  volumeClaimTemplates:
    - metadata:
        name: persistent-storage
      spec:
        storageClassName: azureblob-fuse-premium
        accessModes: ["ReadWriteMany"]
        resources:
          requests:
            storage: 100Gi

allowVolumeExpansion: true
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  labels:
    addonmanager.kubernetes.io/mode: EnsureExists
    kubernetes.io/cluster-service: "true"
  name: azureblob-fuse-premium
mountOptions:
- -o allow_other
- --file-cache-timeout-in-seconds=120
- --use-attr-cache=true
- --cancel-list-on-mount-seconds=10
- -o attr_timeout=120
- -o entry_timeout=120
- -o negative_timeout=120
- --log-level=LOG_WARNING
- --cache-size-mb=1000
parameters:
  skuName: Premium_LRS
provisioner: blob.csi.azure.com
reclaimPolicy: Delete
volumeBindingMode: Immediate

Does anyone encounter the same behavior?

Answer 1

Hello , Welcome to MS Q&A

I think this could be due to the way the storage is being interpreted or displayed by the system. Azure Blob storage is designed for unstructured data and may not directly reflect the same capacity metrics as traditional block storage. The representation of storage size can vary based on the protocol used (such as Blob Fuse or NFS) and how the underlying storage is configured.

If you're using the NFS protocol, the size may be reported differently, and the mount point might not reflect the expected capacity due to the abstraction layer that Blob storage introduces. It’s also possible that the storage class or configuration settings may influence how the size is reported.

The actual storage capacity is 100GiB, but the representation might vary based on the protocol used (such as BlobFuse or NFS) and the configuration settings. This discrepancy does not mean that the storage is limited to 1000M; it is just a display issue.

References:

• Use Azure Blob storage Container Storage Interface (CSI) driver
• Container Storage Interface (CSI) drivers on Azure Kubernetes Service (AKS)

Please let me know if any questions

Kindly accept answer if it helps

Thanks

Deepanshu