RAID Setup for Mac Pro and Video Editing

Hello everyone!

I'm new to the forum and have a question I could really use some help answering. So here goes...

I recently acquired a Mac Pro from a friend to use as my primary video editing computer (I produce commercials and wedding videos). Now, I'm totally new to the mysterious world of RAID and only have a limited understanding so you'll have to pardon my ignorance at times.

The Mac Pro has 3 1TB SATA drives as well as a 120GB SSD drive.

I also recently purchased a 4TB G-Tech G-RAID drive that I was originally using when I was doing my video editing off of my Macbook Pro.

Now here's what I theoretically would like to do or know if this even makes sense to do.

I want the speed and capacity of a striped RAID array within the Mac Pro, but that's not the most secure if a drive goes bad. So I got to thinking...

What if I had my three 1TB internal hard drives in my Mac Pro setup as a striped RAID and then setup a mirrored RAID array to that striped RAID with my 4TB G-RAID drive?

1. Is that possible? Has anyone done it?
2. Does that even make sense to do?

I appreciate your help and guidance!