I never said it was a replacement for a backup. Its redundant storage. The failure of 1 or 2 drives can be tolerated without downtime depending on the RAID level.
SSDs are horribly expensive for storing large amounts of data and you still have failure issues, just like with a hard drive. Plus, they're small so you'd either have to spread the data out and manage what's on what drive, or RAID them into a single volume.
Yes they're expensive, but you've said RAID'd disks are good for simultaneous data access. That's not typically required for either image processing or backups.
Sorry for my lack of knowlege on this subject, but would it be bad to back my photos on a drobo? I was looking at the Drobo s and drobo 5d, which one would you choose and which drives would you buy to put in it? Thanks
It'll be significantly slower as a working drive than a plain old disk inside your computer.
Either way, you should have all your photos on an external disk, stored offsite, say at a friends house. We often see people here in a panic asking for file recovery tools or complaining that they lost all their images and data. Fire, theft, viruses, and stupidity are leading causes of data loss.
The stupider a person is (and I'm not calling anyone stupid), the more backups they need but the less they have, unfortunately.

