Learn the things to know about backup options for virtual machines in Azure

When backing up Azure Virtual Machines (VMs) using Azure Backup, there are several important considerations and options to ensure your data is protected effectively.

Here's what you need to know.

Types of VM Backups

1. Crash-Consistent Backup:

   • Captures the state of the VM at a specific moment, similar to pulling the plug.

   • Ensures disk data consistency but may lack application integrity.

2. File-System-Consistent Backup:

   • Ensures all data on the VM's disk is written to storage before taking a snapshot.

   • Does not ensure application integrity.

3. Application-Consistent Backup:

   • Captures data, memory, and transactions in progress.

   • Uses the Volume Shadow Copy Service (VSS) for Windows and fsfreeze for Linux.

   • Ideal for databases and mission-critical applications.

Backup Mechanism

Backups use snapshot-based technology to create incremental backups after the first full backup.

Initial backup is a full snapshot of the VM.

Subsequent backups only transfer changed data, optimizing storage and network usage.

Backup Storage Options

1. Locally Redundant Storage (LRS):

   • Data is replicated three times within a single region.

   • Cost-effective but not recommended for disaster recovery.

2. Geo-Redundant Storage (GRS):

   • Data is replicated to a secondary region for higher durability and disaster recovery.

   • Provides region failover capabilities.

Backup Frequency and Retention

1. Backup Policies:

   • Define how often backups occur (e.g., daily, weekly).

   • Specify retention periods for daily, weekly, monthly, and yearly backups.

Customize policies based on recovery point objectives (RPO) and compliance requirements.

Recovery Options

1. Restore VM:

   • Recreates the entire VM from a backup.

   • Useful for disaster recovery or major failures.

2. Restore Disks:

   • Recovers individual disks (OS or data) and attaches them to an existing or new VM.

3. File Recovery:

   • Recovers specific files and folders from the VM backup.

   • Ideal for partial data recovery scenarios.

Supported VM Configurations

1. Operating Systems:

   • Both Windows and Linux are supported.

   • Application-consistent backups require Azure VM Agent and integration services for Linux.

2. VM Sizes:

   • Most Azure VM sizes are supported.

   • Ensure VMs have enough resources to handle backup processes.

Security Features

1. Encryption:

   • Backup data is encrypted at rest using Azure Storage Service Encryption.

   • Optionally use customer-managed keys (CMK) for added control.

2. Soft Delete:

   • Retains deleted backups for 14 days to prevent accidental or malicious data loss.

3. RBAC:

   • Role-Based Access Control restricts backup and restore permissions to authorized users.

Costs and Pricing

Backup costs are determined by:

1. Snapshot Storage: Space used for the snapshots in the Recovery Services Vault.

2. Backup Retention: The duration for which backups are retained.

3. Data Transfer: Ingress data is free, but egress charges apply for restores outside Azure regions.

Cross-Region and Zone Redundancy

Azure Backup supports cross-region restores for VMs protected with geo-redundant storage (GRS).

In the event of a region outage, you can restore VMs to another Azure region.

Best Practices

1. Test Restores: Regularly test restore operations to ensure backup integrity and reliability.

2. Use Tags: Tag backups for easier identification and management in complex environments.

3. Optimize Policies: Align backup policies with the criticality of workloads to balance cost and recovery needs.

4. Monitor and Alert: Use Azure Monitor to track backup status and set up alerts for failures or anomalies.

Summary

By understanding these options and considerations, you can design an effective backup strategy for Azure Virtual Machines that aligns with your business continuity and disaster recovery (BCDR) needs.