Hi folks.. I currently work as an IT technician in a school and have been at this game for 25 years. In all that time, I've used all sorts of backup devices and to be honest, there is no one system that fits all.
It depends on what you are backing up. I have a bag with umpteen flash drives, hard drives in caddies, and 5 hard drives with approx 5 Terabyte of space. I now have a google drive account with a 5 Gbyte limit and a Microsoft live account which is 25Gbyte.
Everything is a trade off. You may backup to a backup drive, but have you ever test if the backed up files work if you restored them? What happens if the backup drive fails.
What i do is group thing into critical, not so critical and could live without. All critical stuff goes to the google drive and microsoft live accounts and backed up to school network ;-) The failsafes set up in terms of hardware failures etc is to have critical files in 2 or more locations. Not so critical stuff goes on keypens and backup drives but these are not without problems. I've had the same issues with usb 1, 2 & 3 drives going faulty. Not sure why but critical files are in several locations just to be sure.
I can't give a definitive answer because there isn't one unless you wish to spend big money. Even then you can't guarantee that your backups are safe, secure and most of all, working.
To Grendel. Please tell me you have the 100,000 photos backed up to another location and are not just relying on this one HD!! They do go faulty. Been there, got the teeshirt?!!
Declan