stability problem with iir(4)

[bjoern koenig]

Hello,

there is an Asus PU-DLS mainboard and a Vortex ICP GDT8524RZ+ SCSI-RAID 
controller card. After creating a RAID 5 with three Hitachi Ultrastar 
146Z10 hard disk drives, I installed FreeBSD 4.9-RELEASE and it seems to 
be fine, but after some minutes of doing something hard disk resp. RAID 
access fails. No error message, everything simply stops working; system 
hangs. Kernel is still active, because sending a ping to the 'dead' 
machine will cause a response. If I use FreeBSD 5.2.1-RELEASE I got at 
least a message from iir(4) that the hard disk doesn't respond, but it's 
the same problem. Using another RAID type, e.g. 0, same happens. But 
using each disk as single, I can benchmark the system for hours and 
hours without problem. There is also absolutely no problem if I install 
Windows Server 2003 on RAID, so I suppose it's not a hardware failure.

Does anybody have an idea what's going wrong?

Thanks for help
Bjoern Koenig