I'm running MySQL 5.0.x on RHEL 5.3.
I read in the MySQL Manual (here) that 'it is essential to run the mysqld process with the highest possible priority on the 2.4 kernel to achieve maximum performance' and they recommend using renice -20.
There is no mention of the 2.6 kernel.
On my system MySQL is running with a priority of 0.
I do suffer from load problems where the IOwait gets high when disk activity like copying a big file takes place during normal daytime database traffic.
Is changing the priority a good idea or are there any potential problems with doing this?