Understanding Storage Options in Azure Kubernetes Service (AKS)

Managing persistent storage for applications running in AKS is crucial. AKS provides several options to integrate with Azure's robust storage services, allowing you to choose the best fit for your application's performance, durability, and cost requirements.

Core Concepts

In Kubernetes, storage is typically managed through:

PersistentVolumes (PVs): A piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes.
PersistentVolumeClaims (PVCs): A request for storage by a user. PVs mount into Pods via PVCs.
StorageClasses: Define different "classes" of storage with varying levels of performance and features. This allows for dynamic provisioning of PersistentVolumes.

Azure Disk Storage

Azure Disk Storage offers highly performant, durable block storage for your AKS workloads. It's ideal for stateful applications that require low latency and high throughput.

Azure Managed Disks

AKS can dynamically provision Azure Managed Disks for your Pods using StorageClasses. This is the recommended approach for most use cases.

Performance Tiers: Options include Standard SSD, Premium SSD, and Ultra Disk, catering to different IOPS and throughput needs.
Durability: Data is replicated within an availability zone or region for high availability and durability.
Dynamic Provisioning: Create PVCs, and AKS, in conjunction with Azure, will provision the appropriate Managed Disk.

Example StorageClass configuration for Premium SSD:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: managed-premium
provisioner: disk.csi.azure.com
parameters:
  skuName: Premium_LRS
  location: eastus
reclaimPolicy: Delete
volumeBindingMode: Immediate

Azure Files Storage

Azure Files provides fully managed cloud file shares that are accessible via the Server Message Block (SMB) and Network File System (NFS) protocols. It's suitable for shared access scenarios and applications that rely on file-based storage.

Azure Files Shares

AKS can mount Azure Files shares directly into Pods. This is excellent for scenarios where multiple Pods need to access the same data, like shared content management systems or configuration files.

Protocol Support: SMB (v2.1, v3.0) and NFS (v4.1).
Performance Tiers: Standard and Premium file shares offer different performance levels.
Shared Access: Multiple Pods and even VMs can mount the same file share concurrently.
Dynamic Provisioning: Can be provisioned dynamically using StorageClasses.

Example StorageClass for Azure Files (Standard LRS):

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: azurefile-csi-standard
provisioner: file.csi.azure.com
parameters:
  skuName: Standard_LRS
  location: eastus
reclaimPolicy: Delete
volumeBindingMode: Immediate

Object Storage (Azure Blob Storage)

While not directly mountable as a traditional filesystem within AKS Pods by default, Azure Blob Storage can be integrated with applications using SDKs or through third-party solutions like BlobFuse CSI driver for more advanced scenarios.

Azure Blob Storage Integration

Ideal for unstructured data like images, backups, logs, and large media files.

Scalability: Extremely scalable for massive amounts of data.
Cost-Effective: Generally more cost-effective for large volumes of data compared to block or file storage.
Application-Level Access: Applications typically interact with Blob Storage via Azure SDKs or REST APIs.

For direct mounting, consider the Blob CSI Driver.