Assuming that I am NOT going to add NTFS drivers that allow read+write of NTFS partitions, I was wondering if the choice of filesystem when I partition an external USB drive matters. The choices appear to be HFS+ vs. FAT32.

For the time being, I simply created two half-sized paritions, one of each type. :)

I plan to run various versions of Windows, and keep the VirtualBox files on the external drive.

UPDATE: to clarify-> I'm not concerned about letting my VirtualBox VMs mount this drive, I'm talking purely about using this drive as a place to stick my VirtualBox images, because my main drive is already pre-occupied.

  • Thanks for the suggestions. I'm going to migrate to HFS-only. An additional consideration was that a partition not mountable by normal PC's cannot be a vector for Conflicker. In this specific case, this external drive is technically a "lab" device, I might need to let other people use it. (This does not prevent infection of the guest OS, but it prevents the drive from being a host-to-host vector.) – benc Jul 31 '10 at 6:10


If, as you say, you are not concerned about letting VirtualBox (or a real PC) mount this drive, there is absolutely no reason to use other filesystems.

VirtualBox files are plain Mac OS files, and HFS+ is the "normal"/"native" OsX filesystem, works well, is journaled (=less jamming/crashes) and has no strict filesize limits. Macs feel more "comfortable" on it.

The reason you might consider FAT32 (keeping all files under 4GB) is if you want to be able to boot the same VM images also on a Windows computer (and on the Mac too).

Also, using FAT32 and HFS on the same disk is not that ideal solution as it seems. In order to have Windows PCs see the FAT32 partition, the whole partition table must be of DOS/Win type (Master Boot Record), so you have an HD with a DOS partition table with a Mac HFS partition inside. This is ok but has some limitations like booting (can't use it to boot the Mac). Using a "GUID" (modern Macs) partition table is good for Mac partitions, but your FAT32 partition will not be seen by any PC, making it quite useless.

So.. go HFS+, for the whole disk. Keep a 4GB thumb drive with FAT32 to move files around.


FAT32 has the advantage of being completely cross-platform, but its major limitation is that the files cannot be more than 4GB. This is primarily a problem for working with video, and with virtual hard drives.

VirtualBox supports VMWare's VMDK format. You can use a command-line utility to create VMDKs with the Split2G option as detailed here. It will create separate slices that will grow up to 2GB each. (The GUI creates disks using the native VDI format, which does not do this.)


Windows does not support HFS+ by default. There might be a plugin or something that I don't know about. I know there are ext3 plugins for windows.

If you'd like your USB drive to work with all OS's, it's best to go with FAT32, even though it is old and lacks some features.

  • I clarified my question... There was no immediate need to want the Windows VM's to see anything directly on the USB drive. Its a parking lot for VM's, not storage for the VM environments. – benc Jun 5 '10 at 14:38

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