The PERC6 supports migrating from a single-disk RAID-0 to a 2-disk RAID-1, with the only documented requirement being that you add an additional disk of equal or greater capacity.
You will need OMSA (OpenManage Server Administrator) installed to pull this off - I don't believe the PERC BIOS gives an option for RAID type conversions or expansions. If you don't have it installed, go here and search for a "Managed Node" entry that matches your OS (get the full installer, not the patch).
In OMSA, you can modify a Virtual Disk's configuration with these steps:
- Expand the tree view as follows: Storage > PERC6 > select "Virtual Disks"
- Select "Reconfigure" from the "Available Tasks" drop-down menu next to your existing VD
- Click "Execute"
- Select the disk(s) to be added to the VD, then "Continue"
- Select the desired RAID level, and type the new capacity into the text box (max configurable capacity will be noted below it), then "Continue"
- Review your changes, and then click "Finish"
This info is available in the OpenManage "Server Administrator Storage Management User's Guide". Links for this change frequently, so just web-search the title for a current version. Look for the section in the doc labeled "Reconfiguring Virtual Disks" or something similar.
Note: Your question mentions "adding" hardware RAID. Though your current configuration isn't a multi-disk RAID, the PERC6 is almost certainly still managing the disk as a single-drive RAID0 with RAID config data on the disk and all. So technically this is a RAID config modification, since you're changing an existing Virtual Disk rather than adding a brand new one.
[Obligatory "please ensure you have backups of your data when using ANY type of RAID"]