An important factor in the user experience of any virtual machine is file transfer performance. As we discovered last year, free virtualization software like VirtualBox really lags behind commercial options from Parallels and VMware when it comes to file management, and depending on your workflow, that could be a deal breaker.
This test (like the Virtual Machine Management test later on) is a little different in that it doesn’t include Boot Camp performance. This is because we’ll be testing the process of copying files between the VM and the host operating system, and that activity has no equivalent for a native Windows installation.
Our file tests are divided into two groups: a large file transfer (a single 4GB Windows 10 installation ISO) and a small file transfer (4,096 4KB files). The numbers in the chart represent the time in seconds that it took for each transfer, so a lower score is better here.
Note that unlike our standard tests that rely on computer-generated results, these tests were measured manually with a stopwatch. As a result, we performed each test five times instead of the usual three iterations, in order to minimize the impact of human error. Also note that we rebooted the VMs in between each test to avoid any operating system caching that could artificially improve the times.
Starting off with the large file transfer, we see that the platforms trade victories based on the type of transfer. In the “Within VM” test, which measures a transfer from one location on the VM’s virtual drive, Parallels beats Fusion by a little more than 1 second. When it comes to file transfers between the host and guest operating systems, the “To Host” test (a file transfer from the Windows VM to OS X) shows Fusion and Parallels to be about equal, while Fusion wins by about 3 seconds in the “To VM” test (a file transfer from OS X to the Windows VM).
But file transfer speed can vary greatly depending on the number and types of files, so we wanted to see what would happen if we threw a huge number (4,096) of small 4KB files at our VMs.
With small files, there’s no competition. Parallels 11 wins by a landslide. Things are mostly competitive for transfers within a VM, with Fusion taking about 2.5 seconds longer than Parallels, but when it comes to transfers between the host and the guest operating systems, things fall apart for Fusion. Fusion 8 takes a lengthy, but tolerable, 9 seconds longer to transfer our small files from OS X to the Windows VM, but an astounding 36 seconds longer (a 335 percent increase) when transferring from the Windows VM to OS X. This score is 11 seconds worse than VirtualBox.
We first thought this result was due to a bug or configuration issue, but we verified that there were no configuration factors at play — e.g., encryption, indexing, caching — that would explain it as abnormal. Factor in the poor performance of Fusion 7 on the same test and the conclusion is that Fusion just isn’t very good at transferring lots of small files to the host operating system. Your unique workload and needs will determine if this is a deal breaker when it comes to Fusion vs. Parallels.
It’s important to note that the specific times reported here are all based on the relatively fast flash storage found in all recent MacBooks. The performance of virtual machines stored on traditional mechanical hard drives, or on external storage arrays, was not tested, and may reveal different trends or limitations between the various virtualization platforms.