Backing up all data on ESXi 5.1 server

Hello,

I have a server set up running ESXi5.1 that has two hard drives installed.

Originally i wanted these HDD's RAIDed but my RAID setup is not compatible with ESXi 5.1, so instead I just want to back up the entire contents or one disk onto the other disk. So in the event of the live HDD going boom, I could simply swap them over and carry on from the position where I last backed up.

I have done a bit of research but no solution seems simple and i'm getting a little confused.

If anyone could give me advice or a solution to my problem I would be very grateful!

Thanks,

Max