This is definitely a topic that everyone here should spend some time thinking about. I worked in the IT industry on
computer hardware for many years and know how devistating it can be to a business when all their data is lost. It happens. The only thing you can do is be prepared... redundancy, redundancy, redundancy.
I think portable external hard drives are a bad idea for the general public. Most people don't understand the intricacies of a mechanical hard drive -- as opposed to a flash drive with no moving parts -- and how sensitive they really are. They sell these things now in what appear to be industrial strength cases with rubber bumpers, etc... but no matter how much rubber is around it, drop it once and your data could very well be toast. A hard drive is not something that should be tossed into your backpack or briefcase. There are very delicate moving parts inside that casing. It's a great, fast and very cost-effective backup solution for a small business... but just be careful with it.
Oh... and I've been out of the
computer hardware business for nearly 5 years now, but Western Digital was crap then and it's probably crap now. I keep my client and business files as far away from WD and Fujitsu as possible.
Tape drives are a great solution because your data can easily be taken offsite and stored for safe keeping. The problem with putting all your trust in a RAID solution or even an external hard drive is that the data is left onsite and subject to theft, fire, water or surge damage. Who wants to lug a big external hard drive around with them once a week when you want to backup your data.
An even more popular solution these days is online backups. These can be setup to run nightly, so they won't interfere with your day to day grind and you'll always have a safe backup of all your important data stored somewhere offsite. I assure you, whoever is hosting the backup has plenty of redundancy to keep your data safe.
At any rate, Oliver, you are luckier than you think. You had redundancy. Your data is still safe and that's all that matters. Since that backup drive died, hurry up and get a replacement up and running so you can at least have that level of redundancy. Imagine how you'd be feeling right now if that was your business PC's hard drive that started clicking... and you didn't have a backup drive!
Something to think about.