I have a RAID 1 + hot spare that I would like to reconstruct, online, into a RAID 5 set. I know this is possible with OpenManage, but I has anyone figured out how to pull this off using the MegaCli tools?
MegaRaid Software Guide Page 3-27 has what I think you're looking for.
Note that I've never done this and I don't think that it's a particularly good idea. Make a backup of your data first. Good Luck!