I meant to say you've not benchmarked disk access, and we have no idea what each filesystem is actually doing. Caching performance is "nice", but it says nothing about the actual performance we'd get in real use. Maybe the "slow" fs just exhibits less aggressive caching, which might prove just as efficient depending on the workload. It's definitely interesting to note the huge differences, but I'd really like to see how it goes in "real" conditions...