This content is part of the Essential Guide: Fine-tune your virtualization performance management skills
Manage Learn to apply best practices and optimize your operations.

Don't let antivirus software affect hypervisor performance

Antivirus software has good intentions of protecting your environment, but sometimes can cause a hiccup in hypervisor performance.

Hypervisors have evolved and matured over the last decade, but they can still pose problems in certain circumstances. For example, disk-intensive tasks can impair performance when executed simultaneously on multiple workloads, hardware platforms must be configured to optimize hypervisor behavior, and even hardware subsystems can impact hypervisor operation. Fortunately, many issues are relatively simple and quick to correct, but IT administrators must be able to recognize and correct problematic situations in order to preserve top performance and stability.

How to overcome antivirus software interfering with hypervisor performance

Performance problems can occur when antivirus software is running in the host operating system as well as each virtual machine (VM). As scanning processes hypervisor-related files or folders, like vmms.exe or vmwp.exe, it is possible to disrupt the behavior of related VMs. This can occur because a file is locked when it is accessed by any application -- in this case, the antivirus tool locks a critical virtualization file during scanning, which prevents access by other software, resulting in hypervisor performance problems or even hard errors.

For example, when antivirus software is installed on the host operating system and used to scan hypervisor components, the hypervisor or OS may report a variety of errors. In Hyper-V, you may see errors performing operations on files with user-mapped sections open, or problems with virtual network ports failing to power on because they are not available or aborted I/O operations.

Generally speaking, run antivirus software in the host operating system or in the individual VMs, but not both. If you are not running any other applications in the host OS (the host is only running the hypervisor such as Hyper-V), then do not install antivirus software in the host OS; install the antivirus software in the individual VM instead.

If you are already running applications in the host OS, that may be the best place for antivirus software while foregoing antivirus software in the individual VMs, but be sure to exclude the VM configuration files folder, the VM VHD files folder, the snapshot files folder and core hypervisor elements such as Hyper-V's vmms.exe and vmwp.exe to prevent a dip in hypervisor performance. Remember, you may need to restart the hypervisor manager once exclusions are configured in the antivirus software.

Errors involving user-mapped sections may also indicate a corrupted VM configuration file, which cannot be corrected by restarting the hypervisor manager. Instead, the entire VM may need to be restored from a backup or be recreated entirely.

In addition, it is always a recommended practice to keep the antivirus engine updated with the latest version to ensure best scanning speed and stability.

Next Steps

How to adjust hypervisor settings to ensure optimal network performance

Improving virtual server performance with hypervisor-aware systems

Dig Deeper on Microsoft Hyper-V management