Software raid - mirror? Then you can get off one disk from raid (more safely - then server is down) - that will be your original backup.
Next step is setup hardware raid on controller. You can build raid, if you have one more disk (create mirror). If not - this may be a problem (controllers usually don`t allow to create degraded raid. Take a look at quick init options or another way - is create raid0 volume on controller and trying to convert it to raid1 later (if it possible).
If controller does not support such features, and you dont have additional disk, well, its very difficult to replace metadata of software raid to metadata hardware raid and don
t crush something. :)
If controller have some feature, or you have additional hdd, - just create volume, boot from some livecd/usb/pxe and just copy disk from one mount-point to another. And don`t forget about fstab and mbr.