▁the ▁computer ' s ▁back plane . ▁This ▁allows ▁a ▁single ▁" controller " ▁card — re ally ▁just ▁an ▁interface ▁card — to ▁communicate ▁with ▁multiple ▁dis similar ▁drives , ▁while ▁it ▁also ▁reduces ▁laten cy ▁and ▁noise ▁between ▁the ▁controller ▁and ▁drive ▁hardware . ▁Effect ively , ▁the ▁roles ▁are ▁revers ed : ▁instead ▁of ▁the ▁controller ▁doing ▁almost ▁all ▁of ▁the ▁complex ▁processing ▁and ▁the ▁drive ▁just ▁transfer ring ▁encoded ▁data ▁between ▁the ▁magnetic ▁dis ks ▁and ▁the ▁controller , ▁the ▁drive ▁does ▁almost ▁all ▁of ▁the ▁complex ▁processing ▁and ▁the ▁" controller " ▁just ▁trans fers ▁dec oded ▁data ▁between ▁the ▁drive ▁and ▁the ▁host ▁system . ▁In ▁these ▁systems , ▁the ▁oper ational ▁details ▁of ▁the ▁drive , ▁like ▁head ▁selection ▁and ▁seeking , ▁are ▁entirely ▁hidden ▁from ▁the ▁host ▁and ▁handled ▁within ▁the ▁drive ' s ▁dedicated ▁controller . ▁These ▁became ▁known ▁as ▁" sm art " ▁drives , ▁while ▁ST 5 0 6 - like ▁devices ▁retro act ively ▁became ▁known ▁as ▁" d umb ". ▁ ▁While ▁integrated ▁controllers ▁have ▁many ▁benefits , ▁they ▁also ▁have ▁a ▁dis adv antage : ▁the ▁mechanical ▁drive ▁( called ▁the ▁" head - disk ▁assembly ", ▁or ▁H DA ) ▁and ▁the ▁controller ▁are ▁effectively ▁f used ▁into ▁a ▁mon ol ith ic ▁black ▁box , ▁so ▁that ▁if ▁something ▁goes ▁wrong ▁with ▁the ▁drive , ▁it ▁is ▁nearly ▁impossible ▁to ▁do ▁anything ▁about ▁it — the ▁data ▁is ▁usually ▁irre tr iev ably ▁lost . ▁With ▁a