What about network filesystems? They can be quite fast if you aren't running them over a physical network, such as between host and VM operating system on a si

What about network filesystems? They can be quite fast if you aren't running them over a physical network, such as between host and VM operating system on a single physical machine. My preferred solution to your use case would be to run Linux in a virtual machine, configure the VM platform separately in each host OS to give the guest direct access to a dedicated raw partition in ext4 or any other Linux-compatible format, then serve Samba or some network filesystem to the host from the guest. (Of course, if Linux is your host, you can just mount the dedicated partition directly from the command line or fstab.) Back when Windows was my main OS, I liked Colinux [1], a port of user-mode Linux [2] which allows you to run the Linux kernel as a native Windows binary. But nowadays my first recommendation would be Virtualbox. You could also try qemu, it might have better Mac support. [1] http://www.colinux.org/ http://www.colinux.org/ [2] http://en.wikipedia.org/wiki/User_mode_linux http://en.wikipedia.org/wiki/User_mode_linux