Cynic, repeat after me: "Without RAID I do not have backup." :-)

RAID 1/5 protect against data loss caused by disk failure. It means you get 24/365 backup.

RAID does not protect against users who accidentally delete or unwittingly distort data, it simply ensures that those undesirable states are present in redundant form.

Traditional backup is, therefore, a necessary but often times insufficient adjunct to RAID.

Backup policies provide intermittent snapshots of our data. RAID retains the most current version of our data. Sometimes we need to keep a complete history of changes. This is provided by other systems, such as relational databases and version control software.

'Cynic', a mirrored RAID stores copies of data on the second drive, that means you can back up your data on it (in this case externally) and if a drive fails you can still retrieve it and add a new HD.
And an USB-only drive obviously is not designed to use RAID as a speedup.
Unfortunately that theoretical advantage is lost if firmware updates mess up the whole setup and wipes the data on both drives of course, as a commenter on another forum reported happening to him.
What is 'high availability' suppose to mean anyway? Never mind I guess.

... RAID is not and does not replace backups. RAID is for high availability and/or performance.

A correct factoid or an error ?

LOL!

Okay I had too much to drink.

I also thought the poolparty thingy was hilarious, only wish I had a pool...