Starting with our Apache web-server test profile that is measuring the static HTML web page serving performance, the Red Hat Enterprise Linux 6.0 performance was well behind of where it was at on both systems when running Red Hat Enterprise Linux 5.5. This though is not much of a surprise since it is largely attributed to the default file-system switch of EXT3 to EXT4 between RHEL5.5 and RHEL6.0. However, on the dual AMD Opteron system the RHEL6 performance was ahead of Debian 6.0 but on the Intel system the fastest was Ubuntu 10.04.1 LTS (Ubuntu results aren't available on the AMD system due to a GPU issue) by a significant margin, which is somewhat interesting since each release is using the Linux 2.6.32 kernel and the EXT4 file-system, but Red Hat's enterprise kernel likely has more kernel patches that were back-ported.
As is always the case in the PostMark tests, the switch from EXT3 to EXT4 by default in between the RHEL releases causes a significant performance jump. However, the performance on either system for Red Hat Enterprise Linux 6.0 was not as strong as openSUSE 11.3 with its Linux 2.6.34 kernel.
With the C-Ray ray-tracing test there is actually a slowdown between RHEL5 and RHEL6, but all of the other Linux distributions are running at close to the same pace. This is likely attributed to a GCC regression as noted in other articles between GCC 4.1 (found in RHEL5) and GCC 4.4 found in all of the other tested Linux distributions.
While C-Ray regressed, the POV-Ray performance moved forward between RHEL5 and RHEL6.