Today I eventually started optimizing the performance (thereby reducing server load a bit). It appeared some pages of my larger websites have grown to round about 300 kb causing some latency for lower bandwidth visitor. Having a quite good connection myself, I didn't care about that much in the past. But that's ab pity, because it is very simple to add compression to pure PHP-generated content.

RAID names a concept of using several hard disks as if they were single. It's the abbreviation for Redundant Array of Independent Disks (I guess and wont verify this now). There are 7 or 8 different RAID configuration options, but the most common for desktop PCs are NRAID (JBOD), 0 and 1. This might be because most modern mainboards only support these three. Perhaps they only those 3 modes because that's most common for desktops... however.