Hiya, If you want to have an easy test of db-like access on a filesystem or hardware configuration, try https://launchpad.net/hdlatency which I wrote a few years back. There are no external dependencies, it's simple C. It tests specific sequential as well as random access reads/writes in various block sizes, with and without direct I/O. When used in --quick mode it limits the tests to the specific patterns used by MySQL server. The issue with using a more complex app (PostgreSQL, MySQL, etc) for benchmarking is that you'd need to do very specific tuning on that end also to gain optimal results.
From those filesystems mentioned, extN would tend to be slowest (do set noatime in fstab), and XFS is particularly fast when properly configured. We haven't had any clients use either zfs or btrfs so haven't delved in to that.
Cheers, Arjen. -- Exec.Director @ Open Query (http://openquery.com) MySQL services Sane business strategy explorations at http://Upstarta.biz Personal blog at http://lentz.com.au/blog/