This is a problem, but triple booters are numerically an edge case. Rather, what file format do you use on your portable drives when you use all three operatin

This is a problem, but triple booters are numerically an edge case. Rather, what file format do you use on your portable drives when you use all three operating systems on different machines in different scenarios (say Windows at work, OS X at home, Linux on servers)? I'm sure that starting a virtual machine to share EXT4 drives over the host-only network works (if you have the option of installing VirtualBox everywhere), but I'd be weary of network file system limitations and issues and overall bad performance.