Backups.. the scourge of any form of data-retention =)
A good rule is to as a bare minimum have one master, one backup, one backup to the backup and one off-site backup. This means that the master may fail, and the backup may fail and you will still have one updated backup and one slightly less updated. And if you are travelling or moving, you separate every backup.
And here's the point.. this applies EVERYWHERE. that means if you are on location, you need the same setup including the off-site backup.
Lets take a worst case scenario.. your studio (or the studio/warehouse you are renting right now for the location shoot to store all the equipment) burns to the ground. Thats what the off-site backup is for.
Then lets take a travel scenario. Bag with master in gets stolen, bag with backup in is crashed. Ok. you still have two more. One should probably be in your carry-on luggage. The off-site one you MAIL to yourself. Then you are covering all possible bases. If you loose all four datasources, someones out to get you =)
Sound like a lot of work? Well, reconstructing hard-drive data from a burned/crashed harddrive can cost as much as $1000 per megabyte depending on how much actually can be retrieved. I would say keeping a minimum of 4 datasources (harddrives or some other backup that works) is a lot cheaper and easier.
All this takes is routine. Get your backup-routines sorted out and foremost, make them easy to handle for you. Skipping the backup because you need to rush out the door and just cant be arsed is a good way to loose that days work. Mr. Murphy is not a friend =)
In the end, it can be the difference between delivering that awesome super-shot to your client, or going out of business because you lost all your work.
Oh and some final words on the media. Your average hard-drive (top quality) has a life length of between 3-5 years. This means two things; 1) it MAY fail before that. 2) cycle your harddrives every 3.rd year, OR if one fails, cycle all of them. Especially if you buy your harddrives at the same place then chances are you got a bad batch. This is the same rule btw that you do with every life-protecting securityequipment, when the first unit fails - change all of them.
DVD's & CD's have a life-span of roughly the same thing provided they are handled with extreme care and stored in a dry/sun-less environment. In the jewel-case on a bookshelf in the nice studio is not a good place to store it. Though DVD's are rarely used now simply because of the ammount of data you need to back-up often exceeds the DVD capacity. But still good to know that they are not meant for permanent storage ever, even archive-quality.
Look at your backups not as a permanent solution, ie you shoot, you deliver, you backup, you forget about it. But rather as an ongoing cycling of your information. Keep it active between your backup-systems and for long term storage, online backupservices may be a good idea. But remember to back those up aswell as THEY may not have the same routines you do.
Sorry for the long post here but i have worked with information security and integrity (which includes backuproutines) for the past 20 years so i felt chatty today
Have fun all and keep your backups safe =)