> That's a copy. A backup is something different.
Err no, no it isn't.
Making a clone of a HDD, and putting that clone in your safety deposit box, is a backup.
A backup is just a retrievable redundant copy of the data. A copy on another independent (i.e. not part of the same RAID array) disk in the same chassis is a backup, just not a very good one. Now, you can get much more sophisticated from there, such as keeping many versions (version history) of changed files, and so on. But those are extended backup features, not requirements for 'a' backup. Like with most things, there are degrees of sophistication, cost, security, reliability, level of risk being protected against (drive failure, complete chassis failure, room-wide failure, building-wide failure, campus-wide, city-wide, state-wide, country-wide, continent-wide, finger failure (PEBCAK - deleting a file you didn't mean to)) amongst others that all factor in to how one does a backup or a backup routine.