If in OMV Storage | Disks I select all drives one by one and press the Edit button. Then I set Advanced Power Management, Automatic Acoustic Management, and Spindown Time all to Disabled and save the changes.
When I look in /etc/hdparm.conf I see the following configuration for most of the disks:
However, for three of the disks (all are identical WD Red 3TB) I see this instead:
Note that two of the disks have write_cache set to on, and one is set to off.
Is there something special about these disks that makes OMV override the settings I have made in the Storage | Disks panel? What makes OMV set different values for write_cache on otherwise identical disks?