New Drive install - Intel Rapid Storage Technology?

I have an existing Win7 system that came with RAID installed (a single 1T disk drive) and Intel Rapid Storage Technology. I installed a 2nd, identical hard drive to be used for backups. The mobo recognized the drive, and I booted Windows. I was looking for the format new drive option when to my surprise IRST came up and asked it I wanted to use it to incorporate the new drive (I'm paraphrazing.)

One of the choices is to create a volume and protect data. This sounds like disk redundancy (Raid 1 maybe?) and what I want since I'm not interested in increased performance, but I read elsewhere that adding such to an existing system will erase the existing primary disk. On the other hand, I can't imagine that IRST would offer an option that would damage existing data!

I'm confused and would appreciate any help. Thanks!

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