If this is indeed a PERC 5/i, then the only way you could have made it available to the OS is by making it a single-disk RAID 0.  You must first delete that RAID 0 VD.  What OS do you have installed?  From OMSA, you need to go to Storage, PERC, Virtual Disks, and delete VD1 (your new/second/unwanted) RAID 0, then from the dropdown menu for VD0 (your original/good RAID 0), you need to select Reconfigure ... from the wizard you will select the new disk, select RAID 1 and wait for it to complete the conversion of a single-disk RAID 0 to a two-disk RAID 1.
I have an old PE1950 that I am re-purposing. It has a perc 5/i and one 500GB WD Black. I am done building the OS, configuring the app and now I want to add a second drive to mirror the OS. I am using the 5/i bios. I am able to add the new PD, initialize it and even made it available to the OS, but I can't figure out how to get the 5/i to accept the drive as an acceptable mirror. The drives are both WD 500GB Black SATA. What am I missing? 
How do I setup RAID 1 on perc 5/i