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 don
t have additional disk, well, its very difficult to replace metadata of software raid to metadata hardware raid and dont 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.