Thanks, dibl, for the reply! I don't think that that is really the issue, as it s not a problem when the laptop goes to sleep. When the DU freezes, I can still use the computer with no problems. It seems that this "disk sleep" indicated in htop is about the process, not really that the disk is "sleeping" as whole.
And the drive is an SSD (m.2) in this laptop
# inxi -d
Drives: Local Storage: total: 465.76 GiB used: 70.92 GiB (15.2%)
ID-1: /dev/sda vendor: SanDisk model: SDSSDH3 500G size: 465.76 GiB
Optical-1: /dev/sr0 vendor: MATSHITA model: DVD-RAM UJ8G2 dev-links: cdrom,cdrw,dvd,dvdrw
Features: speed: 24 multisession: yes audio: yes dvd: yes rw: cd-r,cd-rw,dvd-r,dvd-ram
I appreciate your help, though!
If anyone else has any suggestions, please let me know!