As mentioned before, I like to travel light and I backup my photos to a high capacity and tiny USB drive. However, from time to time, I might bring along a portable 1 TB hard drive like this one, just to have some extra capacity available.
The Raspberry Pi series 3 doesn’t have USB ports powerful enough to feed a hard drive, not even a portable one. The exception to that would be a small portable hard drive released by Western Digital some time ago, but it’s not easy to find and only comes in 314 GB capacity.
I found out the best way to connect a portable hard drive to the Raspberry Pi while keeping the arrangement portable and reliable is just by using this little cable. It’s cheap, doesn’t take much space and there is no need to bring along a powered USB hub. Just connect one terminal to the Raspberry Pi, another one to the portable hard drive and the third one to either another powered USB port or a regular USB charger like this one.