I've got 2.5" 2TB Seagate HDD running on my RPi1B+ now, as a storage drive (not a boot drive). The HDD is in a SATA to USB3.0 HDD case
and just last weekend, I booted the latest Raspbian Stretch on an RPi3B+ using a very old 3.5" 250GB HDD housed in a very old 12v powered HDD case...
as the saying goes "...if there's a will ....there's a way..."
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"
Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"