Just to suggest a slightly different tactic - I use a
Drobo for my external disk and plan to use an online, offsite backup solution to back up my drobo. Maybe CrashPlan, but I need to check if they accept data from external drives.
I'm hoping in doing this, all my data will be as safe as can be. The drobo will guard against disk failure, and the offsite will guard against theft and fire etc.
/Doug