I've done it several times. Worst case was on a VAX 8810 running Ultrix. I had to boot off 8" floppies, then load the box from 9-track tape at 6250 bpi. That's just a little over six thousand bits per inch for those not familiar with such low values :-)
All I'm saying is you don't really have a backup plan unless you have tested a disaster recovery restore. Believing the hype of the software and hardware companies is not a plan.
For home users you can live with backups of your documents and image files. For business servers, it can take days to reinstall and configure the OS if the restore software can't do it.