With just 10 pieces of 3090s you are already at 1GH on the Ethash algorithm, why aren't people doing this instead of having so many GPUs around, taking so much space and having to use more risers and more motherboard, why are people not going this way?.
When you have experience mining on RTX 3090 graphics cards, then you will not ask such questions.You need to buy expensive closed cases, make ventilation, change thermal pads. And you will all be in trouble in the summer.
And instead of this, I’ll buy 20 cold 50 MH video cards, let’s say Radeon RX 6700 XT.
I would do the same and the price of such card is not even expensive anymore,sounds like one of the wise choices for 47 Mhsh for card for sure with some new versions going up to 50 Mhsh but 47 Mhsh is a sure thing at 120 watt per card.Three of such cards consume the same or almost the same wattage as a RTX 3090 but have better hash rate in total and of course they run really cool,not only this but all the 6000 series,I own the 6800 XT and can confirm with 35% fan it runs at max 63 degree celsius in 20 degree ambiance temperature.