When dd was born we got an external hard drive so we could back up all the photos and vids in case anything happened to the laptop. Lo and behold the laptop got nicked, we thought "It's ok it's all on the hard drive". Except it's actually failed to back up 4 months worth of videos, for no reason that anyone can work out.
The manufacturers are no help, just say "Unfortunately it sounds as if the data wasn't backed up". And their website says "Our limited warranty does not cover data loss Back up the contents of your drive to a separate storage media on a regular basis". FFS, that's what I bought the bloody hard drive for, to be a separate storage media.
So effectively they're saying this glorified floppy disk might fail at any time, you need to back up to CDs - ie may as well not have bothered getting the bloody thing in the first place.