Andreas, I have an on-board RAID controller in my PC and four external 8-bay SCSI racks. Only one of the racks is 'live' at a time, disks can be hot-swapped within the rack in the event of failure. I mostly use Seagate 350GB disks in the newer racks: best to use identical disks throughout. I've been using this setup for about four years, and in that time have only had two, separate disk failures (both 200GB 10,000RPM Maxtors, oddly enough). I was able to simply replace them, and nothing was lost. The controller and enclosures are Taiwanese-branded items I have only ever seen for sale in HK, China and Taiwan, and they have been very reliable. I don't store copies off site as I'm not commercially dependent on the safety of this stuff, but I would be unhappy if I lost anything! I also store video as well as photos on there, so I need a lot of space.
I have also had too many occurences (in work) of being unable to get tape backups restored, so there's no way I'd use them for my personal stuff. I've also discovered to my cost that CD and DVD media are not as robust over time as we were once led to believe, so for me HDD storage is the only option for now.
RAID 5 isn't quite mirroring - have a look at the table on http://www.midwestdatarecovery.com/raid-array-types.html
to see the differences. You need a minimum of three disks for it; maximum depends on the specifications of your controller.
My biggest complaint about my setup is the noise from the SCSI disks and fans. If I were to re-build this today I'd look at newer setups you can get using S-ATA, and perhaps find a better quality case with improved noise control.
PS - I took a picture of my little girl holding her cat with my 1DsMkII over the weekend - should I expect a visit from the authorities? ::
PPS - David, sorry to hear you've been below par - I wish you good health.