Here is the problem:
1) The drive assignments are not optimal. The exports (or encoded files) should be on a separate disk from the project/capture files disk. Trying to export encoded video to the exact same physical disk as the source media files will slow down the encoding speed, by as much as six times longer.
2) Even the latest platter-based hard drives show practically no benefit whatsoever from SATA 6.0 Gbps. In fact, the fastest such drives do not come anywhere close to saturating even SATA 3.0 Gbps (based on their physical, sequential transfer rates).
3) There were two different P6X58D motherboards. You must tell us the exact, full model number (e.g. P6X58D-E, P6X58D Premium). Strangely, the higher-end P6X58D Premium's SATA 6.0 Gbps controller does not support RAID at all while the P6X58D-E's SATA 6.0 Gbps controller does. Unfortunately, the Marvell SATA 6.0 Gbps controllers steal PCI-e 2.0 or PCI-e 1.0 lanes for themselves, and these controllers typically steal two PCI-e lanes (either PCI-e 1.0 or PCI-e 2.0 - but even two PCI-e 2.0 lanes do not provide sufficient bandwidth for both of the SATA 6.0 Gbps ports to operate at their full speeds). As such, the SATA 6.0 Gbps ports not only have driver issues, but aren't much if any faster than the native Intel SATA 3.0 Gbps ports (this is forced upon due to the fact that the X58 chipset lacks native support for SATA 6.0 Gbps to begin with).
Thanks for the help! I have to rearrange the drive assignment. However, my Encoded Files folders for all projects are all empty. They have sub-folders in them but those sub-folders are empty. Maybe because I use ADL and all encoding is happening in Encore? I am a bit confused here. As for the drives, I appreciate the detailed technical reply. (And you saved me a couple of hundred dollars !)
The exact MB model is P6X58D Premium - thus my original question about speed is irrelevant.
Thank you very much for the prompt reply,