Azure Disk Storage

By Pooja | 8th July 2025

Introduction

As cloud adoption increases, enterprises rely more on virtual infrastructure for their workloads. At the heart of virtual machines (VMs) lies the need for reliable and high-performance disk storage. Azure Disk Storage is Microsoft’s solution to this need, providing durable, high-performance, and secure block storage designed to support a wide range of applications and workloads.

This article dives deep into Azure Disk Storage—its types, features, pricing, and best practices—so you can understand how to leverage it in your cloud strategy.

What is Azure Disk Storage?

Azure Disk Storage is block-level storage designed to be used with Azure Virtual Machines. It provides disks for operating systems, data, and applications. Each disk is a virtualized version of a physical hard drive, which can be attached to a VM.

These disks are persistent, meaning data is retained even when a VM is stopped or deallocated. They support features such as encryption, snapshots, performance tiers, and redundancy options, making them suitable for mission-critical workloads.

Types of Azure Disks

OS Disk

An OS disk contains the operating system for a virtual machine. When you create a VM from an image, Azure automatically creates an OS disk from that image.

Mounted as the C:\ drive (Windows) or /dev/sda1 (Linux)
Typically 127 GiB, but can be resized
Supports auto-encryption by default

Data Disk

A data disk is used to store application data, databases, logs, and other files. You can attach multiple data disks to a single VM depending on the VM size.

Can be formatted with file systems like NTFS or ext4
Available in various performance tiers
Ideal for storing high-IOPS or large datasets

Azure Managed Disks

Overview

Azure Managed Disks eliminate the need for you to manage the storage account used for the disk. Azure automatically handles the storage, availability, and replication.

Benefits

Simplified management: No need to manage storage accounts manually.
Improved reliability: Managed Disks are designed for high availability.
Scalability: Easy to scale as per VM and workload requirements.
Integration: Seamlessly works with features like availability sets, availability zones, and snapshots.

Azure Disk Types and Performance Tiers

Azure offers four main types of disks based on performance and cost:

Standard HDD

Based on magnetic hard disks
Lowest cost option
Suitable for infrequent access
Use Case: Backup, cold data storage

Standard SSD

Entry-level SSD performance
More reliable and faster than HDD
Cost-effective for general-purpose workloads
Use Case: Web servers, lightly used applications

Premium SSD

High-performance SSD
Low latency and high throughput
Ideal for I/O-intensive apps
Use Case: Databases, large transactional systems

Ultra Disk

Highest performance disk
Configurable IOPS and throughput
Sub-millisecond latency
Use Case: High-performance databases like SAP HANA, large analytics workloads

Disk Sizes and Limits

Azure provides a wide range of disk sizes, from 4 GiB up to 64 TiB. Here are typical size ranges:

Disk Type	Min Size	Max Size	Max IOPS	Max Throughput
Standard HDD	4 GiB	32 TiB	500	60 MB/s
Standard SSD	4 GiB	32 TiB	2,000	400 MB/s
Premium SSD	4 GiB	32 TiB	20,000	900 MB/s
Ultra Disk	4 GiB	64 TiB	160,000	4,000 MB/s

You can dynamically scale Ultra Disk performance based on your needs.

Key Features of Azure Disk Storage

High Availability

Disks are locally redundant (LRS) by default
Option for zone-redundant storage (ZRS) for higher availability

Snapshots

Point-in-time backup of disks
Used for disaster recovery or cloning

Encryption

Server-side encryption (SSE) enabled by default
Supports customer-managed keys (CMK) with Azure Key Vault
Disk-level encryption with BitLocker (Windows) or DM-Crypt (Linux)

Shared Disks

Premium SSDs and Ultra Disks can be shared across multiple VMs
Enables clustered applications like SQL Server Always On or SAP

How Azure Disks Work with Virtual Machines

Attach/Detach Disks: You can add or remove data disks dynamically.
Boot from OS Disk: Every VM needs at least one OS disk to boot.
Managed Integration: Azure handles disk resiliency and storage placement.

Mounting and formatting are required after attaching a new data disk. Linux uses /dev/sd*, and Windows shows them as additional drives.

Use Cases

1. Enterprise Applications
Use Premium SSD or Ultra Disk to run critical databases and applications with high IOPS and low latency.
1. Web Applications
Use Standard SSD for backend storage of web apps deployed on Azure App Service or VMs.
1. Backup & Archive
Standard HDD is ideal for archiving infrequently accessed logs and backups.
1. SAP on Azure
Ultra Disks are designed for enterprise workloads like SAP HANA with predictable latency requirements.

Security and Compliance

Azure Disk Storage is designed to meet enterprise security and compliance needs:
- ISO/IEC 27001, HIPAA, FedRAMP compliant
- Integrated with Azure Defender for threat detection
- Disk access policies for fine-grained control
- Private endpoints to restrict network access
Azure also supports double encryption—SSE + Azure Disk Encryption—for sensitive data workloads.

Disk Pricing

Pricing is based on:
- Disk type (Standard HDD, SSD, Premium, Ultra)
- Provisioned size (in GiB)
- Provisioned IOPS and throughput (for Ultra Disks)
- Snapshots and data transfer costs
Example: A 128 GiB Premium SSD (P10) has a fixed price, but you may incur additional costs for snapshots and outbound data.
Use the Azure Pricing Calculator to estimate costs based on region and usage