The sdc disk is one of your cache disks, but the cache disk is not that disk. It appears it is an old assignment in UD that is not for the correct disk. I.e you had a disk in UD that was moved to a cache disk? Or preclear is confusing UD.
Do this:
- Remove the preclear plugin in and see if that disk is removed from UD.
- Then, reboot the server and see if it clears up.
- Delete the /flash/config/plugins/unassined.devices/unassigned.devices.cfg file. You'll have to re-do any UD settings. Reboot the server.