Something is rather odd about the 2 GB IOZone results... for the latest kernels, the write throughput is nearly 2x the read throughput?
In what world do you live in that hard disks can write data so much faster than they can read it? I'm wondering if there's something wrong with the methodology or measurement, perhaps related to ext4 supporting delayed writes?
I think it's important not just to do and publish benchmark results, but also to investigate and understand when the results don't pass the 'common-sense test.' Otherwise, the benchmark numbers are no more useful than a random set of digits.