https://marco.org/2009/01/17/katie-schenk-since-i-got-the-external-drive
Since I got the external drive working I decided to go back and look at some old pictures. […]
Let’s all pray my external drive keeps kicking for that long. Do I need to backup my backup?
Wait… how many physically separate copies of those files do you have? If the only copy is on the external drive, that’s not a backup.
Any hard drive can die at any time. Simply being external doesn’t make it more reliable.
(This is also a good time to remind geeks that RAID is not a backup.)