In terms of the Apache web-server performance itself, that does fluctuate a great deal depending upon the kernel. The best HTTP performance was found with the Linux 2.6.24 kernel where it experiences its biggest performance drop with the Linux 2.6.35 kernel. Over time the performance has fluctuated a fair amount, depending upon file-system module changes, etc. With the Linux 2.6.39 kernel, it is not at a high point compared to Linux 2.6.24 and it is slightly behind the Linux 2.6.38 kernel.
The PostgreSQL performance was interesting with a large increase in the database performance between Linux 2.6.30 and Linux 2.6.32, then falls off a cliff with Linux 2.6.33, and then in Linux 2.6.34+ its pre-2.6.30 numbers have been restored. With Linux 2.6.39, the PostgreSQL performance is right in line with these other kernels.
The PostMark performance exhibits similar performance issues between 2.6.30 and 2.6.32 with the EXT3 file-system on the HDD as like the PostgreSQL results.