Tell me again why we can't have instanced housing?

[Shibi]

to assure the 5-15+ million players who want to be able to leave the game and come back 5 years later that their house is still available.

That's disk space, not server space.

Edit: and simplistically doing the calculation on space

128 bits for an instance UUID
128 bits for an object UUID
24 bits for position <X,Y,Z>
24 bits for rotation <I,J,K>
8 bits for dye

32 bytes. Lets triple that to be generous and add 3 more bytes to hold scale too to allow later expansion.

120 bytes per object. 200 objects = 24KB

Let say 3 houses per person as an average... 72KB per person

15,000,000 players is 1,080,000,000KB / 1,080GB or basically 1TB of data split between 3 data centres. Which is a tiny amount of data.

And that's everyone having 3 houses, each holding 3 times the data that would be needed.

500GB for NA, 500GB for EU, 500GB for JP, 500GB for OCE (My PC has more than this)

I've still underestimated? ok, lets triple it again and add 3 x 500GB SAN arrays in each region.

Teir-1 Enterprise solutions are there for this, complete with hot geo-redundant backup.