Why is RAID 1 considered bad for backup?
There are so many articles slamming RAID (and therefore RAID 1) as being bad backup solutions:
I understand the argument that all the RAID drives could fail, or that a virus could delete all the files on all the hard drives, but I don't see how manually doing what RAID 1 does (copying all files to an external drive) makes any real difference. If the house burns down, all the files on the external drive will also be lost. If your computer gets a virus, it will most likely delete the files on the external drive too. If all the RAID drives fail at about the same time, what's to stop the external drive from failing at about the same time?
Could someone please explain this to me
Answer
RAID is not a backup, it is hardware redundancy for the sole purpose of providing uninterrupted business continuity in the event of a hardware failure. Redundancy is not backup.
RAID is not a backup.
A backup is a solution that allows you to revert to a known good copy of data in the event of data loss. Such losses can be a result of hardware failure, malicious intent, human error, or software bugs. Backup is not redundancy; it cannot provide uninterrupted business continuity.
RAID is not a backup.
Backup and hardware redundancy are two completely separate disciplines with different purposes. Comparing RAID with Backup is like comparing dual tires on a truck with a spare tire.
RAID is not a backup.
A properly managed backup provides for media that is both disconnected and physically separated from the system being backed up. Disconnection protects from malicious intent, inadvertent changes, and electrical/logical damage. Physical separation protects against external disaster such as fire, flood, or theft. RAID cannot provide disconnection. Most implementations of RAID cannot provide physical separation.