Why Do Virtual Machine Backups Fail?

By CIOReview | Thursday, August 25, 2016
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The ease, with which Virtual Machine (VM) backup protects the organization’s virtualized apps and prevents data loss, has enforced data centers to provide foremost priority to Virtual Machine Backup. With more than 80 percent of usage rate in IT field, virtual machine deployment has set a benchmark for itself. Therefore, VM backup plays a vital role in offering easy access to the system. Even after investing time and efforts, IT admins fails to load VM backup into virtual environment. When this happens, it is important to learn the cause of failure. This article elucidates the most common reasons for virtual machine backup’s failure.

Corrupted Backup copy

VM backup failure occurs, when an archived directory maintained by backup software gets tarnished due to the bug. Corrupted directory is enough to cause issues with any backup application. Once this occurs, IT admins must focus on error message displayed in the event log and take necessary action to recreate the catalog based on error message.   

Lack of Accessibility

Executives encounter this issue, when backup software connected to a secured host server needs a service account that can be used to embrace backup process. Such applications are often susceptible to backup failure associated with insufficient access rights. For instance, if the account policy asks for a password change, but backup application itself is not intimidated about change in the password, backup tends to fail before any data being processed, and the event log displays the error message.

Operating System (OS) Version Not Supported

Usage of unsupported operating system may lead to VM backup failure and also cause agent failure. For instance, assume backup applications are inclined to one specific OS, let’s say windows server 2012 R2 might view windows server 2012 as an unconfirmed OS. This issue can be easily solved by confirming, which software does the backup application supports and then taking a step to upgrade VM to a latest OS.

Size of the File Problem

There are some backup software’s that has restriction on the maximum file size that can be backed up; such applications do not go well with virtual machine, having extremely large hard drive storage.

Overloading Host Server

Overloading host server is another issue that leads to backup failure. Suppose a disk that is already loaded with input/output bound is overburdened by storing a virtual machine on it, then it affects the performance of the disk and falls short of time to backup. Over loading of host server can be avoided by rectifying the storage bottleneck.

Virtual Hard disk Corruption

This is very similar to the way physical hard disk gets tarnished. As virtual hard disk gets affected, even backup of virtual machine gets into trouble.  

It is either data integrity error or read error that is displayed on the log that would be the hint to complete virtual disk being hampered.

Volume Snapshot Service (VSS) Failure

Virtual Machine backups run windows server as a guest OS, this usually inclines on Volume Snapshot Service (VSS). This service utilizes collection of writers to assist the backup of different applications and OS components such as Active directory. Failure of any one VSS writer needed for backup process, leads to collapse of complete backup.

If VSS failure is suspected to be the reason for VM backup failure, then verify the state of VSS writers inside virtual machine using VSS Admin list writer’s command.

Error in the App

A human error in the application may lead to the backup failure since it is running on a buggy virtual machine. If the bug is not fixed it further causes restoration failure.

Software Configuration Issue

Security software must be configured regularly to avoid backup failure.

There are many factors that cause VM backup to fail, so when it happens it is wise to start resolving the issue by analyzing the event logs. As a result, admins can rule out critical factors that lead to VM backup failure.