Less fancy, quite often... at least on VPS providers [1]. They like to use reflinked files off the base images. This way they only store what differs. 1: Which

Less fancy, quite often... at least on VPS providers [1]. They like to use reflinked files off the base images. This way they only store what differs. 1: Which is really a cloud without a certain degree of software defined networking/compute/storage/whatever.