Ubuntu 10.04 LTS again had the best disk performance, but CentOS 5.4 and then RHEL 6.0 Beta close behind followed Fedora 12.
If solely counting the number of wins for each Linux operating system where it produced the best numbers, Ubuntu 10.04 LTS had won eight of the tests, CentOS 5.4 won seven, Fedora 12 won three, and Red Hat Enterprise Linux 6.0 Beta won two. However, in many of the tests the performance between Ubuntu 10.04 LTS and Red Hat Enterprise Linux 6.0 was incredibly close where in all but the most demanding environments the performance would be viewed as similar. This though is not too surprising considering both are shipping with similar kernels and GCC versions. The area where the performance seemed to deviate the most between RHEL and Ubuntu was with a few of the disk tests, but overall, the newer EXT4-by-default distributions performed closely. The wins for CentOS 5.4 mostly came down to the tests where the EXT3 file-system is faster than EXT4.
For those concerned about the degraded disk performance, the "nobarrier" mount option can be used with EXT4 (assuming your systems are battery-backed) to recover some of the losses and there are other steps that can be taken as talked about in many of our other performance articles for maximizing the Linux operating system's performance. Also keep in mind that Red Hat Enterprise Linux 6.0 is currently in beta and there may be a few more test releases before the general availability release is made in the coming months. We will be back with more benchmarks as RHEL6 matures, but until then, you may be interested in our Ubuntu LTS benchmarks or our forthcoming Windows 7 vs. Ubuntu 10.04 vs. Mac OS X 10.6.3 benchmarks.