Intel RAID controller RS2MB044 + Intel RES2SV240 expander = doesn't work
The following setup doesn't work: Intel RAID controller RS2MB044, Intel RES2SV240 expander, 16 WD30EFRX (WD Red) hard drives. The demonstrated symptoms are similar to those described here. In our experience slowdown appears with both a RAID6 and RAID5. Perhaps, there is some incompatibility between controller, expander, and drives in any of possible combinations.