Azure VM Backup Strategy

A primary data failure can be caused by any number of factors, from data corruption and software issues to cyber attacks and human error. But whatever the cause, the result is the same: An instant loss of your mission-critical business data.

Luckily, with the right Azure backup and recovery strategy, you can ensure that a data failure suffered by your VMs is nothing more than a minor inconvenience. In this article, we explore what an Azure VM backup strategy is, some important considerations when planning for it, and an overview of the process for both Windows and Linux operating systems.

What Is a Virtual Machine (VM)?

In the field of computing, a virtual machine (VM) refers to a software representation of a computer system. The virtualized environment provides you with the same functionality as the physical machine it is emulating.

In contrast to single-tenant servers, multiple VMs are able to run on the same hardware in what’s known as a “multi-tenant environment”. This is one of the features that make VMs so much more capital-efficient, both in terms of space and maintenance costs.

Can Azure Restore a VM From Backup More Easily Than Physical Machines?

VMs lend themselves well to disaster recovery (DR) and business continuity (BC) planning. Consider the following scenario:

When performing a system recovery in the wake of a major downtime event, restoring physical systems can take anywhere from hours to days. That’s because you must install and configure a new server, install the OS, set up any apps, and only then can you begin restoring mission-critical data.

VM backups are significantly simpler. In fact, they can be restored almost instantly. Azure backup and recovery for VMs is one of the most effective ways to minimize downtime losses, both in terms of revenue and productivity.

Understanding Microsoft Azure VM Backups

Microsoft Azure is a leading public cloud platform, featuring over 200 products and services. One of those is the Azure Backup service. It effectively enables your organization to create backups and recovery points for your VMs across three levels of consistency. These are:

  • File-Consistent
    A snapshot at the file-level of consistency will capture data stored in memory and on virtual disks, in addition to any upcoming I/O operations. File-consistent snapshots are recommended for database apps (SQL, Oracle, etc.) and operating systems.
  • Application-Consistent
    Compared to file-consistent backups, app-consistent snapshots are much more complete. Not only does it ensure write-order consistency, but any apps that are presently running will finish their operations before quiescing.
  • Crash-Consistent
    Crash-consistent snapshots are write-order consistent at the moment a crash or reset takes place. This level of consistency is good enough for non-DB OSs and apps like print servers, Dynamic Host Configuration Protocol (DHCP) servers, and file servers.

Azure Backup Services for Windows and Linux

One of the many advantages of the Azure Backup solution is that it supports an array of both Windows and Linux distributions. But, when it comes to backing up VMs on either OS, the process differs. Here’s what you need to know.

  • Windows VM
    When using a Windows VM, a backup snapshot is taken using Volume Snapshot Service (VSS), otherwise known as Shadow Copy. This snapshot is application-consistent, meaning that it not only captures memory and files, but any pending I/O operations.Because the VM is warned before a backup occurs, the app enters into a consistent and quiescent state. Therefore, in the event that you must restore your VM, this eliminates the chance of data corruption and allows apps to be restored to a consistent state.

Azure Restore a VM From Backup

Source: Christina @

  • Linux VM
    If you’re running a Linux VM, Azure will take a file-level backup snapshot. While this does have the benefit of preventing data corruption, it does not ensure consistency across applications. Because of this, you’ll want to verify that no in-app transactions were interrupted when the snapshot was taken.Note that it is also possible to take Linux VM snapshots that are application-consistent. Simply configure and run custom pre-scripts and post-scripts. You can read more about this framework in the Azure Backup documentation.

There’s one point to keep in mind if you’re using Azure Files for storage: Azure files don’t get backed up alongside your VMs, meaning you must manually enable backup in your Azure Portal. This applies whether you’re working on either a Windows or Linux VM.

Azure Backup and Recovery Considerations for VMs

There are several factors to think about when planning your organization’s Azure VM Backup Strategy. In this section, we discuss seven key factors to consider.

1. Level of Snapshot Consistency

As previously discussed, there are three levels of consistency when backing up VM data in Azure. Crash-consistency aside, you’ll need to ensure your VMs are running for file-consistent and application-consistent snapshots to successfully take place.

2. Schedule VM Backups Separately

You’ll want to backup all of your VMs—just not at the same time. Schedule each VM so that the backup runs on its own. This prevents bandwidth clogging when transferring snapshots to the Recovery Services vault. If you don’t have an existing vault, go to your RS vault and select Create New and follow these instructions.

3. Backup Preparation Time

Preparing backups takes time. In fact, Azure requires up to eight hours to prepare a backup because it must install an extension, spot new changes, and take a local snapshot of the VM.

4. Backup Transfer Time

An initial backup is always the longest. After this, Azure ensures that every scheduled backup job does not exceed 24 hours to completion. In uncongested conditions, you can expect it to take around three hours for snapshots to be transferred to the RS vault which stores all of your recovery points.

5. Restore Time

The rate at which a backup can be restored is a function of the storage account’s Input/output operations per second (IOPS) and throughput. If you do have to restore backup data, opt for a storage account that isn’t presently hampered by a high volume of data requests.

Data Loss Can Happen Any Time

Secure your Azure data with backup services from Atmosera

Find Out More

6. Retention Period

Your Azure VM data will be stored for a specific period, known as a retention period. For each VM, you can choose between short-term retention, long-term retention, and on-demand backup with custom retention. Your choice will be based on operational and compliance considerations. Sign in to the Azure portal to configure your policy settings.

7. Storage Redundancy

Azure Backup storage offers three primary options including locally redundant storage (LRS), geo-redundant storage (GRS), and zone-redundant storage (ZRS). Each of these has its own advantages and limitations. You can read more about each backup option in the Azure documentation.

Get the Right Azure VM Backup Strategy for your Business, With Atmosera

Azure virtual machine backup is the most effective way to protect your organization’s mission-critical data. At Atmosera, we offer Azure backup services for all of your VMs. Whether you want to backup on-premise VM to Azure or develop a bombproof recovery strategy, our Microsoft Gold Certified experts can help. Contact us today to learn more.

Stay Informed

Sign up for the latest blogs, events, and insights.

We deliver solutions that accelerate the value of Azure.
Ready to experience the full power of Microsoft Azure?