[GENERAL] RAID + PostgreSQL?

[MG]

Hello,   we are using PostgreSQL 8.0.3 together with RAID on OpenServer 6.   When we do a big SELECT-query the whole maschine becomes very very very slowly or stands. The maschine has 3 GB RAM, so we suppose it`s the RAID.   Has anyone some experience with RAID + PostgreSQL?   Where does PostgreSQL saves his temporary files? Perhaps these are the reason for the bad performance.   Greetings   Michaela