maps - Does tile server renders every request? -

i trying understand how tile server handle requests.

i red mapnik "creates" map using osm,

does "creates" means every request rendered , returned? if yes performance hit (global map)?

or means mapnik creates tiles needed on initialization , serves right 1 upon request? if yes total storage needed tiles(for global map)?

i trying find way build own tile server (global map) while rendering once.

with typical tile-based maps such osm's default mapnik style, there cache store rendered tiles, contains small subset of possible tiles. other tiles calculated on-the-fly if client tries access them. small percentage of tiles ever requested of them not particularly interesting users.

the openstreetmap wiki's page on tile disk usage has numbers breakdown zoom level. according source, looking @ 50 tb of data if want store tiles global map 18 zoom levels. other estimates range hundreds of tb, though.