Virtual Machine Backup

VM backup definition

Virtual machine backup (VM backup) is the process of backing up the virtual machines (VMs) running in an enterprise environment. VMs usually run as guests on hypervisors that emulate a computer system, and allow multiple VMs to share a physical host hardware system. The most popular hypervisors are VMware vSphere and Microsoft Hyper-V, with other available hypervisors including cloud-based virtual machines.   

As enterprises increasingly rely on virtualization, VMs have become a vital part of enterprise IT environments. Business applications databases, and even containerized workloads run on VMs and generate vast amounts of data that need to be protected using a robust data protection solution. The applications that enable companies to backup and restore all the files that comprise entire virtual machines are called VM backup software.

What is VM backup?

Virtual machine backup is a data protection solution for VMs that performs similar functions to traditional backup solutions that are used physical servers.  Virtual machine backup applications can perform a full backup of all files in a VM, an incremental backup, or differential backup. The vm backup software needs to run frequently and periodically to protect VM files, configurations, and continuously changing data.  Modern vm backup software will utilize enhancement capabilities available through the hypervisor that allow for quicker backups with less impact on the virtual machine.

VM backup concepts

The following are essential concepts to understand the concepts of the vm backup procedures:

• Differential backup – Backup of only the files that have changed since the last full backup.
• File-level backup – Backup that is defined at the level of files and folders.
• Full backup – A backup of all files.
• Full vm backup – A backup of all files that comprise an entire virtual machine, including disk images, configuration files, and others.
• Image-level backup – or volume level is the backup of the entire storage volume
• Incremental backup – Backup of only the files that have changed since the last backup, either full or incremental.
• Quiescing – A process to bring the data of the virtual machine to a state suitable for backups including, flushing of buffers from the operating systems memory cache to disk or other application specific tasks.

What is the VM backup process, and how does it work?

Similar to backing up physical servers, vmbackup protects all the items that are associated with a VM. Virtual machine backups can be performed in many ways, either through a backup agent installed in the guest operating system, or by way of integration from the hypervisor that allows for agentless backups. Regardless of the virtual machine backup process destination, follow careful steps to ensure proper backup and data protection. The main stages of vmbackup include,

• Discovery. One needs to discover the virtual machines in their environment
• Client computer entry. Create a separate client computer entry for each VM
• Mark VMs for backup. Identify the VMs that will be protected and the Virtual Server Agents that will perform the vmbackup process
• Associated disks. Identify the disks that are associated with the VMs marked for backup
• Backup streams. Assign backup streams to proxies in a round-robin sequence
• Download data. Use the virtual server agents to download the backup data
• Snapshot. Create a virtual machine snapshot using the hypervisor API
• Backup. Complete the backup process by saving a copy of the data to another location

Running the backup client inside a virtual machine.

Because a virtual machine is just like a physical machine, it can be backed up in the same manner as a physical machine using backup software running inside the virtual machine.  With this method, the backup agent performs quiescing of the virtual machine being backed up.  This is typically used for file-level backup of the data stored on the disk of the virtual machine.

This method has advantages and disadvantages.  Advantages can be there are no procedural changes or skills required since the backup agent is similar process to that of a physical server backup.  This method can help with consistency of application data for some business critical workloads like databases.  A disadvantage could be higher usage of the hosts resources as the backup operation is being carried out.  However, computer resources today are more capable and the backup software is less resource intensive.

Running the backup client on the virtual machine host machine.

Because a virtual machine is made up of a few files, those files can back up through integration with the hypervisor.  This allows for the files that make up the virtual machine to be backed up as files, but with a few differences.  Since these files are being written to while the virtual machine is running, the VM must be power off, or a snapshot method must be used to backup the files.  This type of backup using snapshots can require quiescing of the virtual machine.  Different operating systems respond in different ways to produce crash-consistent, file-system consistent or application-consistent snapshots. 

If your VM backups include transactional apps such as database and email servers, quiescing them to make sure that they are in a proper state for backup is referred to as application-consistent as an example.  Before a backup starts, the application is paused to ensure that any outstanding transactions and writes are written to disk. This step ensures that the server is aware of the operation and that no data will be lost if VM recovery is needed. Quiescing only works with applications that support the pausing and writing of pending data whenever necessary.

Why is VM backup important?

The amount of data created daily is staggering, and all of it must be stored and protected against loss. By 2025, it is estimated that 463 exabytes of data will be created each day. Users expect to have the data they need accessible and available around the clock. Without virtual machine backup, it is fair to expect some data loss and application failure due to scheduled and unscheduled disruptions. Without vmbackup, many businesses would suffer and lose vital data due to extended disruptions and disaster recovery times. A vmbackup solution keeps the business engines running and brings them back to life faster after outages, ransomware attacks corruption, or any other event that damages their data.

Benefits of VM backup

Digital data and applications are the drivers of business growth. Protecting business-critical workloads and their associated VMs and data is vital for business survival. Data protection provide a safety net against data loss or corruption. Virtual machine backup extends protection to VMs, which are the workhorse of modern IT, but often are overlooked by legacy backup solutions. Backing up VMs ensures your data, configurations, and files’ safety and enables faster recovery after disruptions. Modern vm backup software delivers full VM protection and contribute to business resiliency.