I have a RAID1 array consists of 2 WD Elements USB drives connected to a Raspberry Pi 4.  rutorrent running inside Docker is used for PT downloading.  I occasionally find that the same USB drive LED keeps blinking while there’s continuous uploading activities.  I thought the reading should be evenly distributed among all disks, which is not true.

It is explained on this page that  the live mirror to be read is decided by PID. This becomes interesting when PID of the docker container remains the same before the host or container is restarted. I am not going to restart the docker container regularly, expecting one disk fail before the other..