DL380 G3 SCSI Problem

[John Rowan_2]

I have a DL380 G3, dual 3.06 Ghz Xeon, 4GB RAM.  I had 6 x 18GB SCSI in a RAID5 (1 spare) running in the machine great, was in simplex configuration.  Wanted to deploy with 6 x 300GB RAID 5 (1 spare).  Built machine with CentOS6, patched andn was running great.  Moved to customer site, powered up, 5 hours later drives failed, lost install.  Rebuilt new drives, reinstall, same problem.  Someone suggested trying different controller, couldn't get Smart 3200 to work so reverted to inbedded Smart 5i.  This time changed to duplex configuraiton.  Same drives that were failing now work fine.  Rebuilt server 4 times to see if something to do with installing / patching, no problem.  Rebooted several times, still working.  Left running for 24 hours, no problem.  Any ideas why a simplex RAID 5 would continually fail drives but duplex is running like a charm?