DB Server suddenly overcharges

Steady high load leads suddenly to extreme load

[AcsCh]

When we stress our L(A)MP DB server (X64, 2GB Ram, only for mysql DB used) the Load average is steady around 1 (seen in top), but suddenly it happens, that it goes up to 50-100 and probably more, if we would not stop it.

The reason are usually inefficient querys, or repair/optize operations on our bigger (1GB) tables.

What is strange is that it works "nice" on full load for minutes, but suddenly goes off. Might this be, that certain operations are filing steadily up the RAM, and after some first minutes of "normal 100% operation" the sistem then starts to swap, and runs into some sort of panic?

The problem is less the abouve reasons, where we are "stressing it knowingly" but it happens too in normal operation, when the server is close to 100% steady load.

More RAM might solve it? Or is this something else rather?

Any hint would be very helpfull! Thanks!