I come from an era when unplugging the RAM pack could blow every chip on the ZX80's board, so hot-swappable PCIe cards are just absolute fucking black magic to me.
Yeah, I almost had a heart attack the first time I saw someone do a 'cfgadm unconfigure' && 'cfgadm disconnect'; then pop open the side of a prod box, press a button and pull a card out.
"See, oracle's still running!"
Things like that used to be how one distinguished enterprise hw & sw vs. PCs w/ delusions of grandeur.
We have some Sun V880s at work and I'm fairly sure the only part you cannot change with the power on and system running is the motherboard itself.
And I would not be surprised if some ex-Sun Gandalf Beard "well akshully"s this comment.