I used SuperDuper for a couple of years, but abandoned it a couple of years ago because I was keeping SD copies of the main hard drive on separate internal hard drives. When I made changes to the main drive, SD would sometimes change the copies, too, and I didn't want that. I finally went to Time Machine that does keep things isolated to the internal backup drives. I change which drive I want to back up to and do it. It maintains its integrity. I told the SD folks why I was changing. They may have made modifications to correct the problem, but I'm now hooked on Time Machine and will probably stay on it for the foreseeable future.
