Ubuntu becomes slow after huge file move during Deep learning

I'm using Ubuntu 22.04. While I'm moving huge dataset (over 200GB) from SSD to HDD, my PC becomes slow after around 1 hours later. At the same time I'm executing Deep learning program(it becomes stop after same hour). I checked CPU, RAM and IO but there are no problems. Some command works fast(ex ls) but others are not(ex apt). And also the reboot speed becomes extremely slow.