If you're looking for a clone of your system drive I wouldn't be looking for a single clone unless you want minimum downtime. In that case RAID1 might be better.

I'd be looking for a tool that clones the disk to an image file. You then have to run a tool to restore that image file usually from some kind of recovery disc you make. That way allows you to have multiple system images. Those system images could then just go into your Crashplan backup store to be deduplicated.

Tools like Acronis can do incremental/differential type backups. I wouldn't recommend Acronis though after fighting to get a refund after proving it didn't work properly.

Having a single clone copy to another identical disk provides only one backup in time. That may be acceptable to you though.