ZFS and EXT4 came out ahead of UFS on FreeBSD when it came to the Threaded I/O Tester. We began by looking at four threads of 64MB writes, where OpenSolaris had the lowest latency followed by Ubuntu and then Fedora 12. However, several times slower than Linux/OpenSolaris were the two FreeBSD operating systems. The latency for OpenSolaris was half that of Ubuntu 9.10, but was just a tenth of FreeBSD's.
When upping the thread count to 32, there was a smaller difference between OpenSolaris and the rest, but still the OpenSolaris time was cut in half compared to FreeBSD with UFS and just slightly faster than EXT4 on the Linux distributions.
EXT4 ended up having a huge advantage over ZFS and UFS when it came to performing random writes with the Threaded I/O Tester. This test continued using 64MB writes with 32 threads. Ubuntu and Fedora did shockingly better, but for those unfamiliar with the Phoronix Test Suite, tests are generally ran multiple times (including Threaded I/O Tester) for accuracy.
Changing from writs to reads, 32 threads of 64MB reads had positioned the five operating systems to performing more close to one another. Ubuntu 9.10 was in first while Fedora 12 was in second place by just a microsecond lead, followed by FreeBSD just a few more microseconds later. In this test, FreeBSD 8.0 had a modest improvement over FreeBSD 7.2.