Based on your system specs and the Asrock website, you have the Z68 Intel chipset. So, if you go into device manager, you should see something listed under controllers, such as ICH10R or so. I see no mention of a third-party controller in the board specs, so that's it. Intel chipsets are good, in terms of soft-RAID, but overall, your performance will be less than what you'd expect to see with a single drive. Soft-RAID has some overhead resource utilization because it isn't an actual hardware chip handling the RAID functions. You got mad in another thread when I tried to describe that to you. I'm not saying that to stoke any flames, just pointing out a previous conversation on the topic.
Now, how much slower would it be? That depends on a lot of factors. However, you should be able to run a standard disk benchmark on it. I would expect to see them perform around 75% to 80% of what a single WD Black drive would run.