External Hard Drive replacement/RAID

I currently have a 1.5TB external drive connected to my HR21 HD DVR but recently overall system speed has slowed to a crawl, all recordings when watched are jittery with dropped frames and I am afraid my hard drive is dying.

I would like to change my external drive to a hardware raid case for data protection but would also like to keep my existing recordings/schedule. Is it possible to clone my existing external drive to a new drive and retain the recordings and playability? If so, is there a certain program I need to use to maintain the proper drive format?

Thanks.