This would not be surprising at all! An impressive amount of work has gone into making the Linux VFS and filesystem code fast and scalable. I'm well aware that Linux didn't invent the RCU scheme, but it uses variations on RCU liberally to make filesystem operations minimally contentious, and aggressively caches. (I've also learned recently that the Linux VFS abstractions are quite different from BSD/UNIX, and they don't really map to eachother. Linux has many structures, like dentries and generic inodes, that map to roughly one structure in BSD/UNIX, the vnode structure. I'm not positive that this has huge performance implications but it does seem like Linux is aggressive at caching dentries which may make a difference.)

That said, I'm certainly no expert on filesystems or OS kernels, so I wouldn't know if Linux would perform faster or slower... But it would be very interesting to see a comparison, possibly even with a hypervisor adding overhead.