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I'm planning on installing Windows on my Mac, and would like to be able to use both Boot Camp (for when I need to be able to use all of the hardware of the computer) and a virtual machine (for those times when I don't want to restart).

I noticed that both VMWare Fusion and Parallels allow you to set up a virtual machine which uses the Boot Camp installation, which is exactly what I want because I want to have one installation of all the programs.

However, I'm wondering if using a virtual machine with the Boot Camp installation has the same exact performance as creating a brand new virtual machine.

The thing that prompted me to think that they might not have the same performance is the marketing text on VMware Fusion's website:

Boot Camp Improvements — Up to 5x faster disk performance with Boot Camp virtual machines and a new option to disable authentication.

... which I understood to mean that, in the past, a normal virtual machine (i.e. one that doesn't use Boot Camp) was faster than one that uses a Boot Camp installation, and now with the upgrade, it's 5x faster... yet it's still not as fast as the normal virtual machine (since then they would probably mention that it's now as fast as a traditional virtual machine).

Is there a performance difference when using a normal virtual machine vs. one that uses a Boot Camp installation in VMware Fusion or Parallels? If so, which one is faster and by how much?

Update: Since there are two attributes to compare, the wording is a bit confusing.
For clarification, let:

A = Performance of normal VM on VMware Fusion 3
B = Performance of Boot Camp VM on VMware Fusion 3
C = Performance of normal VM on VMware Fusion 2
D = Performance of Boot Camp VM on VMware Fusion 2

I understood the marketing text to mean B = D * 5, and I inferred A > B since they mention that Boot Camp needed improvements, and rather than saying it's now as fast as a normal VM, they give a "5x" figure.

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Yes, B = 5*D is what the sentence was saying, but I don't think that you can safely assume A > B. Intuitively, I'd expect a VM based on an actual disk partition to be faster than a VM as there are fewer levels of abstraction, and I think that the sentence is just saying that it's even faster than it was before. –  Kyle Cronin Dec 29 '10 at 18:31

3 Answers 3

As I use it on regular basis I can say it's good performance of using Bootcamp installed windows via VMWare Fusion 3.

Here is process I followed.

  1. Make a bootcamp partition using Bootcamp Assistant for the space.
  2. Install the Windows XP version.
  3. Open the VMware and select the bootcamp partition, when you create a new virtual machine for Windows.
  4. VMWare installs few utilities on the bootcamp partition, to use it to boot via Fusion.
  5. Once all this is done, you can launch this windows version like a normal virtual machine in Fusion.

If I want a lite usage of windows I will boot via Fusion, if I want to run heavy programs then I will boot into Bootcamp, but I rarely does it, as Fusion VM is 99% OK for me for all activities including development with Eclipse.

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I have exactly the same question, and have yet to find a good answer. In the past (before Fusion 3.1), I understand that a virtual disk was generally faster, because: a) this could take advantage of host cacheing, etc. and b) Fusion still had to tunnel through the host OS to access the Boot Camp partition, since the hard drive is really "owned" and managed by the host. I'm not sure what changed in 3.1 to increase the performance by 5x, but apparently it can now access the BC partition much more efficiently.

In my case, I actually have a second physical hard drive in my Mac Pro that is dedicated to Windows. So, theoretically, Windows could talk directly to this hard drive without going through the host OS at all. I'm not sure that Fusion is actually able to recognize this special case and do that, but it would be awesome if it did, similar to the way the guest OS can "own" certain USB devices.

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A Boot Camp VM is slower for two reasons: the NTFS driver used is slower than whatever a normal VM uses, and also, the Boot Camp partition is placed on the innermost (slowest) section of the hard drive platters.

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