Booting from backup

[guruuno]

I today, bought this program to do a backup of my OS X.
After doing a backup (Sandbox), I was not able to boot from the backup.
(The backup is on an external USB Maxtor One Touch III hard disk).
Reading here in the forums, it says that Mac's cannot boot from external USB hard disks.
Is this true? (I am a Mac newbie)
I could have sworn that I did boot previously from an external USB HD.

I just want to make sure the backup is valid befor suggesting to my customers that this is the 'program of choice' for backups.

My major consideration is to have a backup process in place that offers the same type of protection that Acronis True Image does, or Symantec Ghost, and Symantec Backup Exec (formerly Symantec LiveState Recovery & before that PowerQuest V2i).

That is, bare metal recovery, bootable rescue media to access the backup image to restore to a new or old hard disk, mountable images to inject or extract files, scheduling, full backups and incremental (only files that changed since last backup), and the ability to store backup images to media sizes for DVD archicing (4.7Gb).

Am I asking for too much, does ANYTHING exist?

IF the Mac is to become a major competitor, and I belive it will, it will need the same or similar apps to compete with Windows apps, especially for Disaster Recovery/