transition through portal takes too long, i am attacked by mobs on the other side before i can do anything about it.

this issue started back in December when i changed my hard drive because my original ssd failed. so now i have an old hard drive and everything has become much slower. i didnt think this would effect gameplay but maybe I'm wrong. so when i use a portal to go to the nether i can hear stuff happening from the other side but im still in the transition where the terrain is being built so i cant do anything to respond. meanwhile mobs attack me and i die before i have a chance to defend myself.