Azure Virtual Machine Disks

This document provides a comprehensive overview of disk management for Azure Virtual Machines (VMs). Understanding how to manage VM disks is crucial for optimizing performance, ensuring data durability, and controlling costs.

Types of Azure Managed Disks

Azure offers several types of managed disks, each with different performance characteristics and cost implications. Choosing the right disk type is vital for your application's needs.

1. Premium SSD (Solid State Drive)

  • Best for: Production and development/test workloads requiring low latency and high throughput.
  • Features: High performance, consistent latency, suitable for I/O-intensive applications.
  • Tiers: P1, P2, P3, P4, P6, P10, P15, P20, P30, P40, P50. Performance scales with disk size.

2. Standard SSD

  • Best for: Workloads that require consistent latency at an affordable price, such as web servers, lightly used applications, and test/dev environments.
  • Features: More consistent latency than Standard HDD, lower cost than Premium SSD.
  • Tiers: E10, E15, E20, E30, E40, E50, E60, E70, E80, E90.

3. Standard HDD (Hard Disk Drive)

  • Best for: Workloads that are not sensitive to latency, such as backup, non-critical batch jobs, and archival.
  • Features: Lowest cost per GB, suitable for large amounts of data where performance is not a primary concern.
  • Tiers: S10, S20, S30, S40, S50, S60, S70, S80.

Disk Operations

You can perform various operations on Azure VM disks using the Azure portal, Azure CLI, Azure PowerShell, or REST API.

Attaching and Detaching Disks

You can attach data disks to a running VM or when creating a new VM. Detaching a disk is also a common operation, especially when migrating or decommissioning resources.

Note: You must stop (deallocate) a VM before detaching an OS disk.

Creating and Managing Snapshots

Snapshots are point-in-time copies of a disk. They are stored as read-only blobs and are independent of the original disk. Snapshots are useful for backups and disaster recovery.

# Example: Creating a disk snapshot using Azure CLI
az snapshot create --name myVMDiskSnapshot --resource-group myResourceGroup --source myVMDisk

Creating Disks from Snapshots or Images

You can create new managed disks from existing snapshots or from platform or custom images.

Disk Encryption

Azure Disk Encryption (ADE) provides full-disk encryption for OS and data disks at rest. It integrates with Azure Key Vault to manage encryption keys and secrets.

Security Best Practice:

Always enable disk encryption for sensitive data to protect it from unauthorized access.

Performance Considerations

The performance of your VM disks directly impacts application responsiveness. Key metrics include IOPS (Input/Output Operations Per Second) and throughput (MB/s).

  • Understand the IOPS and throughput limits for each disk type and tier.
  • Monitor disk performance using Azure Monitor.
  • Consider using Ultra Disks for extremely demanding workloads (preview).

Cost Management

Disk storage is a significant cost factor for Azure VMs. Optimize costs by:

  • Choosing the appropriate disk type for your workload.
  • Deleting unattached disks and old snapshots.
  • Using Azure Hybrid Benefit for Windows Server and SQL Server licenses.

Tip:

Review your disk usage regularly and right-size disks to avoid overspending.

Further Reading