On a multiplayer realm, I tried to avoid strip mining and probably only mined maybe a stack of diamond ore. I did however run a very successful shop, selling whatever I farmed. Through these methods I got a total of 17ish stacks of diamonds.
On my first world (which I mentioned in this thread 7 years ago) I've filled nearly an entire chest (half a double chest) with diamond blocks, 1,705 to be exact, plus two more in the floor for a total of 1,707 (the stats say that I've crafted 1,708, with 9 diamonds crafted so one block was uncrafted; nowadays I consider all crafted mineral blocks to be permanent). Amazingly, most of this was mined without using Fortune, which I stopped using after my first post (I'd crafted 453 diamond blocks and mined about 2,100 ore by then, with 6.6 times the ore mined but only 3.7 times the blocks crafted since then; conversely, I've since stopped using mined diamonds to repair my gear since I get it all by trading now):
I've also mined 13,826 diamond ore, plus taken hundreds of diamonds from minecarts, which is just a small fraction, 0.525%, of the more than 2.6 million ore that I've mined in this one world alone, including 1.75 million coal and 640,000 iron, plus hundreds of thousands of non-mineral resources (rails, cobwebs, moss stone, representing around 650 mineshafts and 1,750 dungeons, plus 3,668 spawners mined since I enabled the stats for them). I also have many other worlds, some with more than 1/4 as much ore mined, and have easily mined more than 20,000 diamond ore in all my time playing:
This is a cutaway view of my storage room; each corridor can store nearly half a million resources as blocks and I've filled three of them with coal, plus another with iron and nearly one with redstone (I have well over 3 million resources stored due to the multiple drops from redstone and lapis, plus other items like chest loot, rails, moss stone, and cobwebs):