Backing up your computer is important. However, many view it as difficult, complicated, expensive, or all the above. The truth is, creating a good backup system doesn’t have to be any of these things. Stephen Hackett
For my iMac, I have an external 500GB external disk to back the internal SSD via Time Machine. I have separate external FireWire 800 drives for Documents (500GB), Photos and Video (2TB), and iTunes (1TB). My Adobe Lightroom Catalog is on the Photos & Video drive. I backup each external disk to another 5TB external FW800 drive using CrashPlan. The entire 5TB drive is backed-up to the cloud via CrashPlan.
These multiple backups reduce the risk of a single point of failure. If the internal SSD fails I can boot and run from the Time Machine drive until I get a replacement or I can recover from the Time Machine drive.
Using CrashPlan and the backup from the external 5TB drive I can recover data for any of the other drives should they fail.