I have two Pelican cases. One for hard drives, and another for transporting USB sound interfaces, cables, hubs, MIDI keyboard/drumtriggers, etc. Both have double padlock holes.
The small case I use for hard drives holds two 3.5" drives side-by-side, and if necessary, I could carve out two or four narrow slots for storage of backup SSDs edgewise.
But I need to start including backups for my laptop, NAS, and future server(s) (to be built later this summer), so the small case is not going to cut it for much longer. I'll have to get a bigger one that will be able to support as many as four 3.5's and four to six 2.5's, plus boot-DVDs or thumbdrives with recovery software.
That's another key: Don't forget to size your disaster recovery case appropriately to include room for boot media; and maybe even two copies at that. And regularly use that boot media to be sure it still works (especially if one of them is on optical media).
Someday I will get an airline-sized Pelican case sized for airline overhead compartments and capable of carrying camera and music controllers, etc. My needs are just weird enough that I probably can't use the foam-insert cases; will probably have to go with a reconfigurable soft-divider version.