whats the purpose of the little holes on some hard drives with the "do not cover this hole" text near them anyways?

it’s a tiny, filtered air intake. hard drives have to be enormously protected as the internals are incredibly delicate

however

the holes have less to do with airflow and more to do with making sure the pressure inside the enclosure matches the pressure on the outside. completely sealing them wouldn’t work: the pressure at a manufacturing plant in taiwan at sea level is much greater than the pressure in, like, denver colorado meaning a drive could very well explode or implode given cases like that

in fact, serious commercial-grade drives used in high altitude areas are specially-compensated to deal with the altitude. since they’re higher up in the atmosphere, the air is a lot thinner & the atmospheric pressure is correspondingly lower. this is problematic:

the disc platter inside the drive is spinning fast. the edge of the disk is traveling about 75 mph. as the platter moves over the air beneath it gains lift. exactly like a wing on an airplane. this moves the platter up or down, closer or farther away from the read/write head. this causes at best read/write errors and disk fatigue & at worst head crashes

hard drives are crazy pieces of engineering