Here is the current official guidance on how to shrink your array: https://docs.unraid.net/legacy/FAQ/shrink-array/
Our Current Scenario:
There are 2 options when it comes to removing drives, and both are very involved with multiple (9 or 17 steps + 5 subnotes) steps and involves updating your disk configuration list manually which risks data loss if the user mistakenly swaps a data disk as parity, or puts a pool drive in the wrong slot.
Additionally, this FORCES the user to start the array with it warning them if they messed up, they risk data loss (without knowing necessarily if they messed up before the array starts).
Request:
I would want a simple "disk removal" button in the instance there are 0 reachable files on the disk (no shares data). I, as a user, can manually move all my files off of the disk to be removed, and once complete, I can stop the array and remove the disk via. the GUI. As simple as:
Move all files from the disk you wish to remove to other disks in the array
Once all files are removed, and looking at the disk content shows 0 files or shares, stop the array
Click the "remove disk" button next to the disk in the array"
Start the array
Where the user does not have to be concerned with disk configurations or risking assigning a disk incorrectly resulting in data loss.
Request (Stretch Goal)
I, as an UNRAID user, would want the ability to mark a disk from the array as "to be removed", where UNRAID will automatically move files off of that disk.
Once there are 0 files remaining on the disk, UNRAID would
(Option 1): Automatically remove the disk and populate it as an unassigned device while the array is still running
(Option 2): When the array is shut down, check the contents of the marked disk and if there are 0 share files, move it to an unassigned device.
(Unsure on backend technical limitations for removing a disk from the array while in a non-stopped state or checking the folder structure of a disk while in a stopped state).
-------------------------------------------------
(In case the link updates, current instructions on how to clear array):
1. The "Remove Drives Then Rebuild Parity" Method
2. The "Clear Drive Then Remove Drive" Method