RAID is not backup

As I have written in other postings, a RAID setup consists of 2 or more harddrives, which are mirrors or contains the same data. It is done in a way, that if 1 disk fails, no data is lost and the system will continue running.

But why do I say that RAID is not backup, then?

1. RAID 1-5 can save your data if 1 harddrive fails. If another disk fails before you can replace the bad disk and the data can be mirrord, you have lost all of your data.
2. RAID only protects against drive failure. Theft, water damage, virus, accidential deletion etc. will still cause you to lose data.
3. RAID does not protect against RAID failure. If the controller, the hardware which manages the disks, fails you will lose all of your data. And trust me: They do fail. Even the very expensive ones.

Note that RAID 6 will allow you to have 2 drives fail before data loss, but: You are still not fully protected.

All in all: RAID will let your server or computer run without interruption if a harddrive fails, but it will not protect you as a backup should do.