Virtual Machine Performance Myths, Debunked

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Guest blog by Mervin Christopher, Parallels Support Team


Note: This blog post was written prior to the release of Parallels Desktop 11 and contains screenshots from Parallels Desktop 10. The points are applicable to both versions of Parallels Desktop. Thanks for reading!

 

Let’s say you use your virtual machine for online trading software, but it takes a long time to log in to Windows and start the actual application. Or, maybe you prefer to run video-editing software in a virtual environment. Or, like many others, you use Parallels Desktop to run Microsoft Office and it takes forever to launch. Sound familiar? Chances are that you have too few or too many resources dedicated to your VM.

How many resources do I need to allocate to my VM? If I max out the resources, will it make my VM faster? These are the kinds of questions many users regularly ask the Parallels Support team, so I thought I would shed some light on the matter by dispelling three common myths about VM performance.

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Myth 1: The more processors I assign to my VM, the better.

It sounds logical—more is better, right? Wrong.

One or two virtual CPUs is enough for most of the Windows applications you run. Assigning three CPUs can even slow down overall performance, especially if you have an older Mac model.

To see how many CPUs are assigned to your VM, launch Parallels Desktop and make sure your VM is shut down. Go to Virtual Machine Configuration > Select the Hardware tab > CPU & Memory.

You can then configure the amount of processors (CPUs) to provide the appropriate number of computing resources for the workload you plan to run in the VM.

Virtual Machine Performance Myths in Parallels Desktop

In most cases, one or two CPUs provide the best performance. Assigning several CPUs to your virtual machine may be required if outlined in your Windows program system requirements, but it also depends on your actual Mac hardware.

If you aren’t sure if the application you want to run on your VM requires more than one CPU, test it with either one or two CPUs assigned.

I performed a small test on my MacBook Pro with 2.5 Ghz Intel Core i5 Processor and 8 GB of RAM using Parallels Desktop 10 for Mac and Windows 8.1 installed in a VM:

Virtual Machine Performance Myths in Parallels Desktop

First, I allocated 2 CPUs and 2 GB of RAM to the VM and opened Microsoft Office 2013 and Auto Desk Revit Architecture 2015. It took a reasonable amount of time to open these applications, and overall performance was just fine. I could easily switch between Mac and Windows applications—no “hangs” or slowdowns. Then I increased it to 4 CPUs (RAM stayed at the 2 GB level). It took almost 50% more time to open Windows programs and the overall performance of Mac dropped significantly.

Here are some numbers:

With 2 CPUs assigned, Windows login took 16 seconds, Microsoft Office 2013 opened in 4 seconds, and Auto desk Revit architecture 2015 took 24 seconds to launch.

With 4 CPUs assigned, Windows login took 22 seconds, Microsoft Office 2013 opened in 8 seconds, and Auto desk Revit architecture 2015 opened in 30 seconds.

Myth 2: Maxing out my RAM makes my Windows VM run faster.

When you create a VM on your Mac, Parallels Desktop allocates a certain amount of RAM by default to your VM—the allocated amount depends on how much memory you have on your Mac and the user profile you’ve chosen during setup.

In my test, the amount of RAM affected overall performance. I also didn’t notice significant performance improvement by changing the default RAM amount to run Microsoft Office, Internet Explorer, and other basic applications.

I used the same MacBook Pro with 8 GB of RAM for this test. I opened some basic programs like Microsoft Office and a few heavier applications like Autodesk Revit Architecture and a game called Burnout Paradise. The best performance was indicated when the VM was assigned between 2 GB and 4 GB RAM memory. Maxing out the RAM slider to 6 GB adversely affected the performance and start-up time by almost 60%.

Virtual Machine Performance Myths in Parallels Desktop

The green section on the RAM slider indicates the recommended range and is detected in accordance with your Mac resources. Try to avoid going into the yellow or (especially) red zone—this could cause not only your Windows side to slow down, but your Mac side as well.

Myth 3: My “heavy” apps will run faster if I increase the video memory.

Believe it or not, you can actually adjust the video memory in the Video pane of the VM configuration window. To do so, go to your virtual machine’s configuration > Hardware > Video > Video Memory.

I would recommend setting the amount of video memory depending on specific Windows applications requirements. If you use graphic applications which require high video memory usage, set it in accordance with system requirements.

I did a test by installing two different heavy applications, the Burnout Paradise game and Autodesk Revit Architecture on my Windows 8.1 VM. Initially, I assigned 256 MB of RAM video memory, started the game and it opened slowly with the screen flickering. Why? The game’s system requirements were not met with that amount of video memory.

Then I went ahead and assigned 1 GB of video memory and tried to play Burnout Paradise again. This time, the performance was good, with clear video and no major lags.

The same thing happened when testing Autodesk Revit Architecture—it looked blurry and took more than 30 seconds to start with 256 MB of video memory. Once I increased the video memory to 1 GB, it was faster and opened smoothly within 20 seconds.

I played with the different video memory settings and it turned out that assigning video memory between 512 MB and 1 GB was the best for my test. Note that I was running “graphics-hungry” programs—I wouldn’t need to increase the video memory for basic applications like Microsoft Office.

Virtual Machine Performance Myths in Parallels Desktop

When I assigned 2 GB of video memory for my test the VM slowed. I can’t blame the VM for this—the Mac itself didn’t have enough available resources, and 2 GB was in the “red zone” in this case. So, as a result, assigning as much video memory as possible doesn’t always increase the performance—it can actually degrade it.

If you’re running 3D programs in the virtual environment, I recommend adjusting a few more settings.

To configure 3D settings, go to VM’s configuration > Hardware > Video and select ON or select a version of DirectX (10 or 9) from the 3D acceleration menu. Make sure Parallels Tools is installed before enabling these settings.

You can also visit our Knowledgebase to learn more about improving your VM’s performance.

We hope these tips and tricks were helpful—and don’t forget to follow the Parallels Support team on Twitter!

Parallels is the #1 solution for running Windows on Mac for over 10 years. Curious to see if your specific non-Mac application can run through Parallels Desktop? Feel free to try it out yourself—download a free 14-day trial.

 

Social Media Lead for Parallels WorldWide Support. Passionate about technology and customer experience.

  • Brandon Champney

    Hi, new to parallels, getting it soon. Will be running SolidWorks on Windows 7 a 3D cad program. It only uses one cpu so I am good with that. My question is my video card has 1500 mb ram and I have 16 gb system ram. Parallels pro allows you to set up to 64 gb vram which I’m not too clear about. Do I set my vram according to the video ram that I have or the system ram? Would it benefit me to get parallels pro instead of the basic parallels? Thanks

  • Brandon Champney

    Hi, new to parallels, getting it soon. Will be running SolidWorks on Windows 7 a 3D cad program. It only uses one cpu so I am good with that. My question is my video card has 1500 mb ram and I have 16 gb system ram. Parallels pro allows you to set up to 64 gb vram which I’m not too clear about. Do I set my vram according to the video ram that I have or the system ram? Would it benefit me to get parallels pro instead of the basic parallels? Thanks

    • Hi Brandon,

      In regard to your comment, “Parallels pro allows you to set up to 64 gb vram”, the term “vram” refers to virtual RAM, not video RAM. Apologies for the confusion there. Onto your question about how to set your virtual RAM – leave the video RAM setting for your Windows 7 virtual machine at the default, at first.

      You should only increase the video RAM setting if SolidWorks won’t launch or performs poorly.
      The memory for video RAM for the virtual machine comes out of your system RAM, not out of the RAM on your video card. Similarly, leave the RAM setting for your Windows 7 virtual machine at its default setting. You should only increase it if performance of SolidWorks is low.

      Note that increasing the RAM setting of Windows 7 too much will result in poorer performance of Windows 7 and the Mac OS.

      And finally, in regard to your question on purchasing Standard vs. Parallels Desktop Pro, it’s hard to predict. Certainly Parallels Desktop Pro is the safer choice, and one benefit is that you will be on a subscription (so you’ll never miss an OS update, etc. as long as you continue to renew your subscription), but SolidWorks should work fine on Standard. If performance on the Standard version is too low, we can help you test to see if Pro would increase performance – just let us know.

      Hope that helped!

      Lindsay

  • Riccardo Cambo

    Hi, pretty silly question, if I dedicate 3 on 4gb of ram for Windows, when Parallel is closed I can only use 1gb ram for mac or It split only when parallel is open?

    • Hi Riccardo – the memory allocated to a virtual machine is only used when that virtual machine is running. However, we don’t recommend allocating 3 GB to a VM on a 4 GB Mac – you run the risk of “starving” your Mac of RAM, which could cause your entire Mac to run slowly. Just an FYI. Thanks for your question!

  • Bob

    If this is true then why does it take windows 10 (under latest parallels version) 18 seconds to boot to login with 4 cores and 28 seconds to boot to login with 2 cores?

  • Henry H.

    Hi, was wondering. is it possible that allocating too LESS ram memory for a vm will slow down the whole computer?

    also, when is a vm not using the ram? if its just open but no programs are running, will it still keep it all? and what about suspended mode?

    • Hi Henry!

      If a VM is not allocated enough RAM, the VM itself will be slow since it is constantly swapping in and out the required bits of code. This constant disk activity could conceivably affect other applications that are trying to access the disk.

      When a VM is started, its allocation of RAM is dedicated exclusively to that VM. This RAM is unavailable to other Mac apps or other VMs. Even if the VM is doing “nothing”, this RAM is still unavailable to other Mac apps or other VMs. When a VM is doing nothing, the use of the CPU is basically zero, but the RAM is still exclusively dedicated to the VM.

      Unless you have quite unusual needs in the VM, you should use the default amount of RAM. This will give you the optimal performance both in the VM and in the Mac.

      Hope that helps. Thanks!

      Lindsay