It's allegedly common knowledge that a file is only as good as its verified backup. I work on the basis that if I don't have at least two backup copies of an image or video, I have no integrity at all. My workflow is as follows;
1. Copy the files from the device or memory card to a hard disk inside the computer. For me, this is a Mac Pro with four internal drives, one dedicated to unedited media. 2. Import and add the files to my editing program catalog. For images that is Lightroom and I maintain a separate copy of each image. For video it is Final Cut Pro and it links to the original. 3. Back the original drive and the LR directories up daily to an external drive. In my case this is a Drobo S drive array. 4. Use a cloud service to backup both the original files and the Lightroom repository. I strongly recommend Crashplan. 5. Verify each backup daily and do a test restore of random files from the cloud weekly.
This works pretty well for me. The riskiest piece in my current workflow is the Drobo. While it is very cool technically, I've had a lot of trouble with the Drobos that I own and when they next die, I will replace them with an alternate solution. I am presently leaning towards a Cal Digit array.
The other important consideration is the quality of the physical drives you buy. Drobos are extraordinarily hard on drives so I have a stack (literally) of drives that have died before their time when used in a stressful environment like a Drobo. My greatest success has been with Hitachi disks. I have never lost a Hitachi, and note that Apple uses them as the internal drives in their desktop machines, indicating some level of serious testing. I have also had good to very good success with Western Digital Caviar Black drives. Western Digital has recently released a new series of disks called Red that are suited to NAS (Network Attached Storage) solutions available in 1TB, 2TB and 3TB versions. I have no experience with them personally, but initial reviews look positive. Western Digital Velociraptor drives are superb but VERY expensive for home use.
I cannot say similar good things about other drives. Yesterday I had two more Seagate Barracudas do their impersonation of Ontario roadkill, bringing my total stack of dead cudas to five. There are three more still in production and I will replace them as quickly as I can afford to do so. I have never had a Barracuda larger than 1TB make it halfway to its Mean Time Before Failure number and do not recommend Seagate drives to anyone. They used to be excellent, but not so lately. While I appreciate the eco-friendly idea behind Western Digital Caviar Green drives, I cannot recommend them either. The Drobos eat Caviar Greens like they are candy. While you can likely pull the drive and reformat it in a standalone enclosure for short term use, this is risky based upon my personal experience.
I would strongly suggest selecting drives that run at 7200rpm and having a large onboard cache. The Hitachi drives I am buying now are all 7200rpm drives with 64mb cache. Good luck!