Cesar,
> On this server I have only one database with 312GB of data. The database
> had run fine during 4 months, but from two months ago, during high work
> load periods, the server is collapsed by "%sys" type load.
Hmmm. Have you updated Linux any time recently? I'm wondering if this
is a PostgreSQL problem at all. It sounds like an OS issue.
Can you give us the results of mpstat -P ALL 3 ? The dstat output
doesn't tell me much.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com