Raid question on Mac Pro

My Mac Pro currently has 2 drives. The main drive with OS and Apps and then I have a 2nd 1TB drive with my all my clients images for my photography business. These images are backed up on disc, but the 1TB drives is my working drive. I was thinking about setting up a raid and add a second 1TB drive to back up the other. I am new at Raid and not sure what is the best option. Also, if I do this will I lose speed performance when working with the images in Photoshop CS4?

Implementing RAID will add resilience to your system, but RAID is not a substitute for proper external backups of your data.

Before you decide on a RAID level, first determine if you have a READ-intensive environment or a WRITE intensive environment.
It's a balancing act and depending on the RAID level, you might see a performance increase in READ operations and take a hit on WRITE operations.

Also cost efficiency can be considered as RAID 5 is more cost efficient than RAID 1

When possible, go for a hardware implementation of RAID, not a software implementation.

If you google for it, you will find very usefull information and user experiences.

Hope this helps.
Cheers
McBie