How to Improve VMware VM Performance

When VMware Performance Requires Improvement

The main reasons to diagnose your VMware VMs and try to improve their performance are:

  • A VM’s performance is reduced compared to that of an identical machine running on another host.
  • Apps are running slower than intended. The apps’ performance is okay when a VM is moved to a different host.
  • Apps take too long to launch.
  • Applications suddenly stop responding or fail to launch.
  • CPU, RAM or disk load reaches 100% and stays at that level.

VMware Performance Issues and How to Fix them

VMware VM performance may decrease due to either software or hardware problems. Here, we will review VM performance problems connected to CPU and RAM, storage, snapshots, network and software. The explanation on solving those problems will be provided as well.

CPU and RAM

One of the most common reasons for VMware VM performance to degrade is the lack of hardware resources. If a VM does not have enough CPU resources, then that VM is unable to run apps smoothly. To solve that issue, enable the VM to utilize additional CPU cores or more virtual processors. Additionally, if your processor has fewer than 4 cores, not enough cache, and low clock speed, consider the hardware upgrade for your host.

Storage

Storage system performance is critical to ensure the high performance of the VMs storing virtual disks on that system. VM performance heavily depends on storage latency. Using a Solid State Drive (SSD) is recommended when storing VMs. When it is not possible to use SSD disks, 7200 RPM or 10000 RPM HDDs (Hard Disk Drives) should be used. A 5400 RPM HDD is too slow for VMs to function properly. Disks with SAS interfaces are preferred in VM environments.

Snapshots

Virtual disk snapshots reduce virtual disk performance. A new delta VMDK file of a virtual disk is required for each snapshot. Each data VMDK contains the change log with data differences from a parent VMDK file. The VM reads that data when interacting with the VM disk. That means the VM reads data from multiple files on the same physical disk simultaneously, and thus VM performance decreases.

VMware Tools

VMware Tools is a set of utilities and drivers used to improve user experience and boost VM performance. Therefore, the guest OS should have VMware Tools installed to increase overall graphics performance, synchronize a mouse, use VMs without lags in a fullscreen mode, among other improvements.

Network

With an ESXi host connected to a Storage Area Network (SAN) or Network Attached Storage (NAS), the network overload or network speed deficiency can reduce VM performance. For high performance, separate the networks in your environment:

  • vMotion network
  • ESXi management network
  • Storage network

Antivirus Software

The host’s antivirus scanning virtual disk files can reduce VM performance. To solve the issue, exclude VMDK files in VM directories from the antivirus scanning list.

Hyper-V Troubles

VMware VM performance can be reduced when you use VMware Workstation versions 15.5 or newer, which support running VMware VMs when the Hyper-V feature is installed on a Windows host. Hyper-V then uses Intel VT-x and AMD-V hardware virtualization features directly. For VMware Workstation with a Virtual Machine Monitor (VMM) that must run in privileged mode, those features are not available when Hyper-V is installed. VMM runs in the user mode instead to ensure compatibility, and cannot utilize the CPU’s hardware virtualization features.

Performance Monitoring: Avoid Bottlenecks

By regularly monitoring the performance of your VMs, you can solve issues proactively and maintain production stability. With VM monitoring, troubleshooting the exact cause of a performance problem can be done quickly. However, the key is to monitor VMs on the host level instead of a guest OS. Guest operating systems might show incorrect data as they are not virtualization-aware.

Summary

In this post, we covered the main reasons for VMware VM performance degradation and quick ways to troubleshoot them. To ensure the maximum performance of your VMs and host, you need hardware with an appropriate performance envelope, balanced RAM distribution, and proper software configuration.

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NAKIVO is a US-based corporation dedicated to developing the ultimate VM backup and site recovery solution: https://www.nakivo.com