Machine running out of RAM

Hello!
I've got 2 Machines, 2xAMD Opteron 2GHz, 6GB RAM, 600GB (3disks) HW RAID-5.
One of 'm runs realy nice, but the other one not good.

When writing to the RAID device it's real slow, I dont have any real numbers but cus' it might be buffering but no way near 40-50MB/s.

After leaving the machine to copy 10GB lokaly it runs out of memory and prints some stuff about swap stats and "cold plug" stuff IIRC, and some programs that dies due to no memory left.

The funny thing is that it says that it is 13GB swap left wich is the total swap size.

Something is really ill.

The RAID controller is a 3ware sata raid card and is identical to the one in the other machine, which works fine.

My suspisions are on the raid card but any one who have any other ideas or how to trace down the causing error?

Best regards, David.

Tell me about the server model.
Is it a SUN v40z?

No it's a Arima motherboard with Opteron CPU's.
Running 32bit, cus' VMWare did'nt run no good with 64bit linux.