Azure Images and Snapshots
By Pooja | 17th July 2025
Introduction
In cloud computing, backup and replication are fundamental to system reliability, disaster recovery, and scalability. Microsoft Azure offers two essential tools that help achieve these goals: Snapshots and Images.
Whether you’re trying to preserve the current state of a virtual machine (VM), automate mass deployments, or recover quickly from failure, Azure Images and Snapshots allow you to capture, reuse, and replicate VM disk states efficiently.
In this article, we’ll explore the concepts, differences, use cases, implementation strategies, and best practices for using Azure Snapshots and Images effectively in your cloud infrastructure.
What is a Snapshot in Azure?
A Snapshot in Azure is a read-only, point-in-time backup of a managed disk. It captures the state of a disk at a specific moment and allows you to restore the disk to that exact state later.
Characteristics:
- Applied to OS or data disks
- Full or incremental
- Stored in Azure as a managed resource
- Can be used to restore a VM or create a new disk
Snapshots are disk-level entities and are typically used for backup, rollback, or migration scenarios.
What is an Image in Azure?
An Image in Azure is a complete copy of a VM (or just the OS disk) that can be used to create new virtual machines. It is commonly used in automated provisioning or mass deployment scenarios.
Characteristics:
- Can include:
- OS disk only
- OS + Data disks
- Based on generalized (sysprepped) or specialized (configured) VMs
- Supports Shared Image Gallery for scaling deployments
- Used for golden image creation and rapid replication
Images are intended for creating many VMs from a common baseline.
Snapshot vs Image: Key Differences
Feature | Snapshot | Image |
Scope | Single disk (OS or data) | Entire VM (OS + optional data) |
Purpose | Backup or recovery | VM replication or deployment |
Reusability | For disk recreation | For VM creation |
Types | Full / Incremental | Generalized / Specialized |
Includes Configuration | No | Yes (based on image type) |
Automation Use | Limited | Ideal for scale-out deployments |
When to Use Snapshots
Use snapshots when you need:
- Temporary backup of a VM or disk before making changes
- Rollback capability for patching, updates, or configuration changes
- Disk-level replication to another region or subscription
- Quick restore points for testing or recovery
Snapshots are faster and simpler than full backup tools and are suitable for short-term retention.
When to Use Images
Use images when you need:
- To create multiple VMs from a common configuration (golden image)
- To scale out your application in a consistent, predictable manner
- Persistent configuration, software, and services preinstalled
- Custom VM templates for development, production, or hybrid workloads
Images are perfect for DevOps and Infrastructure-as-Code (IaC) workflows.
Creating Snapshots in Azure
Via Azure Portal
- Go to the target disk of a VM.
- Click + Create Snapshot.
- Enter name, resource group, and snapshot type.
- Choose Full or Incremental.
- Click Review + Create.
- Via CLI
bash
CopyEdit
az snapshot create \
 –name mySnapshot \
 –resource-group myResourceGroup \
 –source /subscriptions/{sub}/resourceGroups/{rg}/providers/Microsoft.Compute/disks/myDisk \
 –location eastus
- Go to the target disk of a VM.
- Click + Create Snapshot.
- Enter name, resource group, and snapshot type.
- Choose Full or Incremental.
- Click Review + Create.
- Via CLI
bash
CopyEdit
az snapshot create \
 –name mySnapshot \
 –resource-group myResourceGroup \
 –source /subscriptions/{sub}/resourceGroups/{rg}/providers/Microsoft.Compute/disks/myDisk \
 –location eastus
Via Azure Portal
- From a VM (Specialized Image)
- Deallocate the VM.
- Go to the VM → Capture.
- Choose specialized or generalized.
- Create the image.
- Via CLI
bash
CopyEdit
az image create \
 –name myImage \
 –resource-group myResourceGroup \
 –source myVM
- Using Shared Image Gallery
For mass deployment and replication across regions:
- Create image definitions and versions
- Distribute images to multiple regions
Generalized vs Specialized Images
Type | Description | Use Case |
Generalized | VM is sysprepped, user-specific data removed | Mass deployments, DevOps pipelines |
Specialized | VM state is preserved, including credentials | Quick clone of a specific configured VM |
Important: Generalized images can be reused broadly; specialized images are tied to a single state and user configuration.
Shared Image Gallery
The Azure Shared Image Gallery is a repository service that allows you to:
- Organize and version images
- Share images across regions, subscriptions, and tenants
- Deploy thousands of VMs using custom images
- Enable replication for high availability and compliance
This is ideal for large enterprises and service providers.
Use Cases
Disaster Recovery
Take snapshots before updates or configuration changes
Restore VMs quickly in another region using snapshots
DevOps Pipelines
Build generalized images with code and deploy on demand
Compliance and Standardization
Use golden images with pre-installed antivirus, logging agents, etc.
Test Environments
Clone existing VM configuration using specialized image
Limitations and Considerations
Snapshot | Image |
Cannot boot directly | Must be attached to a VM |
Cost based on disk size | Cost based on image storage size |
Incremental snapshots require same region | Generalized images require VM deallocation |
Encryption state must be matched | Encryption is preserved |
No automatic retention policy | Requires versioning in Shared Image Gallery |
Integration with Azure Backup
While snapshots are manual and intended for short-term, Azure Backup is designed for:
- Scheduled backups
- Long-term retention
- Policy-based restore points
Use Azure Backup for compliance and enterprise-level backup strategies and snapshots for quick checkpoints.
Cost Management
Azure charges:
- Snapshots: Per GB per month
- Images: Based on the size of source disks (premium or standard)
- Shared Image Gallery: Includes replication and storage costs
Best Practices
- Use incremental snapshots to save storage costs.
- Always sysprep your VMs before creating generalized images.
- Organize image versions in Shared Image Gallery with semantic versioning.
- Apply RBAC to control access to images and snapshots.
- Use tags and naming conventions for lifecycle management.
- Monitor snapshot expiration or deletion schedules manually.
- Encrypt snapshots and images using Azure Disk Encryption (ADE).
Conclusion
Azure Snapshots and Images are vital components of a well-architected cloud environment. Snapshots provide point-in-time disk backups that are fast and efficient, while Images provide VM templates for replication, scaling, and standardization.
Understanding their differences and using them correctly can lead to:
- Improved reliability
- Faster deployment
- Better disaster recovery
- Consistent DevOps automation
In a world where infrastructure agility is paramount, mastering snapshots and images gives you the power to back up, scale out, and standardize your virtual environments effectively.
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