Improve virtual machine performance on Mac

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There might be multiple possible reasons for low performance, for example:

The Basics

Virtual machine performance is directly related to a computer's hardware resources. It is also very important to allocate even shares of hardware resources between the host operating system (macOS) and guest (VM) according to the recommended system requirements of both systems.

Note: starting with version 14, Parallels Desktop for Mac brings a new feature: CPU Usage Monitor. Look at the VM window tray and CPU Usage Monitor will light up in red when CPU usage in Windows is above 70%. Click on CPU Usage monitor to see what processes in Windows use the computer's CPU. Clicking on a process name will open Windows Task Manager showing selected process:

The computer's performance mostly depends on several hardware components: CPU, RAM, and hard disk. While CPU cannot be replaced at hand, most of Mac computers enabled for RAM and hard disk upgrade.

Upgrading Your Mac with a Solid State Drive

If your Mac uses a hard disk drive (HDD), it is highly recommended to replace the drive with a solid-state one (SSD). This is the #1 recommendation for all Mac users which gives the significant performance boost to Mac at 2-3 times. Contact your local Apple Authorised Service Provider to get assistance with the disk replacement.

TIP: you can check your Mac's drive type at 'System Information' report (click  > About this Mac > System Report... > Hardware > SATA/SATA Express)

Upgrading Your Mac with Better Memory Modules (RAM)

If you notice in Activity Monitor that your memory pressure is up to the maximum, it's time to check if your Mac allows you to do RAM replacement with higher modules capacity.

Visit these articles for more details:

Checking Software Settings


  1. Make sure that you have ample free disk space on your startup disk. Visit this article for more details: KB 123553.
  2. Use Activity Monitor to check what unwanted applications consume a high percentage of system resources (CPU and Memory).
  3. Make sure Time Machine backup is not taking place while you’re running the virtual machine. The backup process may slow down overall system performance.

Parallels Desktop Preferences

  1. Make sure you're using the latest build for your Parallels Desktop version:

    • On the macOS menu bar click Parallels Desktop icon > Check for Updates.... Download and install the updates if available.
  2. Store your virtual machine within Mac HD (internal storage). Running a VM from external USB disk or NAS may significantly lower VM performance.
  3. Be careful running several virtual machines at once - each VM consumes considerable amount of resources and may slow down overall computer performance.
  4. Try disabling antivirus on the Mac side. Alternatively, you may add adding Parallels Desktop/virtual machine location to a white list that antivirus maintains of known good software.

Virtual Machine Configuration

  1. Shutdown your VM > open its configuration > switch to Hardware tab > CPU & Memory > make sure that the number of processors (CPUs) selected is not maximum (e.g. 4 out of 4). In most cases, half of total CPUs will provide optimal performance. Assigning more than a half of CPUs for the virtual machine may cause performance degradation for both Mac and VM.

  2. Make sure that memory allocation is within the recommended level. Similarly to processors, best practice is to assign half of Mac's total RAM.

    NOTE: The amount of memory assigned to a virtual machine must be multiple of 1024 or Windows may behave inappropriately. E.g 1024, 2048, 3072 MBs and so on.

  3. Under Advanced settings make sure that 'Parallels' hypervisor is selected.

  4. Under Hardware > Graphics set Memory option to Auto (Recommended).

  5. Under Options > Optimization set Resource usage to No limit.

  6. If your Mac uses an HDD or a Fusion Drive (not SSD), make sure that the option TRIM is disabled: go to Hardware > Hard Disk > Advanced Settings > uncheck Enable TRIM option.

  7. Start your virtual machine and test performance.

Possible solutions for Windows virtual machines

  1. Install all pending Windows updates. Then restart a virtual machine two-three times to apply changes completely.
  2. Users who use their virtual machines rarely may encounter slowness and other performance issues after starting a virtual machine if it hasn't been used for a long time. From our side, we recommend giving Windows some time to finish doing necessary internal jobs and other required maintenance tasks. If Windows still working slowly, check Task Manager as described below to find out the reason for CPU consumption.

    The virtual machine's CPU consumption directly depends on guest operating system usage. If you notice that your virtual machine consumes a high amount of CPU resources, check CPU consumption in the guest operating system in Task Manager (right-click on Windows taskbar > Task Manager):

    Once you determined what process of Windows program consumes a sufficient amount of CPU, you may refer to the software manufacturer's knowledge base to find more information. For some types of software, like video or photo editing, CAD, or video games, high CPU usage is a common operating condition.

  3. Try to run a clean boot to exclude possible third-party applications influence. 
    Note: in step 3 keep Parallels services enabled. 
  4. Try checking a Windows virtual hard drive as described in KB115549.


Perform defragmentation on your Windows virtual hard drive as described here

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