Something that tends to get lost in talking about data backup and recovery is the sequence of events that create the backup and events that can corrupt that process.
As in the case of the RAID setup, it did what it was supposed to do...keep a copy of the data from drive1 on drive2. The problem here was two-fold, the data was lost/overwritten and THEN the second drive simply duplicated the missing/overwritten data.
So, everyone starts talking about keeping copies on another machine, using off-site storage and other wonderful ideas. However, if the user came along right AFTER the data was overwritten and made a copy and stored it off-site they would still have a copy of nothing.
Backup is not just about multiple copies, it is about ensuring data integrity throughout the process. Not only do you have to copy the data, you have to check and make sure that it is indeed the data you want and that it can be restored in a timely manner.
There are many horror stories of IT departments that have a multiple/redundant copies of their critical data (including those wonderful tapes) and when disaster strikes they find out that all of their tapes, drive images, and other data backups are somehow unusable.
