[CentOS] Centos/Linux Disk Caching, might be OT in some ways

Hi,

> If you want a fast database forget about file system caching,
> use Direct I/O and put your memory to better use - application
> level caching.

The web application is written in PHP and runs off MySQL and/or
Postgresql. So I don't think I can access the raw disk data directly,
nor do I think it would be safe since that bypasses the DBMS's checks.