After installing the plugin I tried spinning down drives and nothing seemed to be different from before the plugin was installed, i.e. Normal errors and drives not actually spinning down. I uninstalled and reinstalled (as well as a reboot) but the plugin still doesn't seem to be working at all.
There are no SAS Assist entries in syslog on either manual spin-down or Unraid's spin-down, Only the normal barrage of errors.
One thing to note is that command line spin-down of the drives is working using:
sg_start -r --pc=3 /dev/sdX
and starting back up again with:
sg_start -r --pc=0 /dev/sdX
So I'm sure the issue is somewhere on the OS side and not the communication with the disks or the disks themselves. I cannot think of a reason that the plugin wouldn't even show in any of the logs like all other logs I've seen in this thread. I have done a couple migrations in the life of my install including about a week ago after the server had been off for about 150 days (had to update everything recently) if that is of any relevance. I can confirm the install of the plugin.
Please let me know of any other information that might be helpful!