i am tested using two scenarios,
1) First, i am used switch2osm for tile rendering. its good it handles many things. But it takes long days to pre-render all tiles and it takes huge memory in TB.
2) Second, i am used tilemill to generate MBTiles and served using https://github.com/chelm/mbtiles-server But i dont know how much efficient for larger using.
Other than this, Is any other way serving Tiles for whole planet in efficient way.
Machine config : 1.5 TB and 128 GB main memory.