storage space vs stacks

storage space and stacks both are nouns.

Word	Noun	Adjective	Verb	Adverb
storage space	Yes	No	No	No
stacks	Yes	No	No	No

As nouns, stacks is a hyponym of storage space; that is, stacks is a word with a more specific, narrower meaning than storage space:

storage space: the area in any structure that provides space for storage
stacks: storage space in a library consisting of an extensive arrangement of bookshelves where most of the books are stored

Other hyponyms of storage space include cache, cellar, wine cellar, closet, cupboard, drawer, cellar, root cellar.

storage space (noun)	stacks (noun)
the area in any structure that provides space for storage	storage space in a library consisting of an extensive arrangement of bookshelves where most of the books are stored
	a large number or amount