Should add here...
I have 4 sources I back all important data to.
1. My 2x 320GB HDDs in RAID1
2. My NAS enclosure, has 2x 640GB HHDs in RAID1
3. My 500GB external drive. regular 500GB 3.5 HDD, IcyDock enclosure. I only use it when I am normally out and about.
4. My UbuntuOne cloud service. Only save mostly pictures on there.
Here is my Backup
Drive C which has pretty much Just Apps and crap on my desktop
Drive D Has videos and a folder called tech files which document wise is all things important
Drive F This has isos and setup files for Office / Windows and other stuff
Drive S is a nighty backup drive for all things D (Get it? haha)
Office Site Backup 1-1 / 1-2 are 3TB drives put into a sata dock once a month and rotated in a safety deposit box (The switch is done at the bank, both drives are never at my house, car or moving in the same location at 1 time, except for when I switch them out at the bx) which backs up c, d, and F and G
Carbonite, Backs up all documents, desktop and the tech files folder on Drive D
DVD copy of tech files once a month also in my safety deposit box.
Quickbooks Laptop SSD Drive - Is a laptop just for quickbooks and NOTHING else, No web Browsing , just quickbooks and Windows updates. It is accessed via Remote desktop via my main 4 Monitor workstation and my dual monitor couch computer.
The Quickbooks company file on the laptop is backed up nightly on Drive D (which is then backed up to carbonite and monthly to the 3TB backup drive and a DVD), my couch computer both over the network as well as a USB drive plugged into the laptop each one storing 14 different versions.