I see this setting now on Unraid 12.6.3. It seems to me that it would be extremely helpful to implement compression per user share, which seems to me to align more with how humans sort content, and then to be implemented as per path as the user shares are laid out on the underlying disks. Is this on the radar? While one could do this per disk and shuffle the media accordingly, that seems to add implementation complexity for the end user, such that adding an extra 500GB drive might be a solution one choses, rather than setting compression on an existing 8TB drive...by enabling compression on a share holding highly compressible books and documents. As such, approaching the feature with this user-share-centric thought may also reduce barriers to adoption.
i.e.
Disks 1-6 (each, individually would show...) FS BTRFS: Compression is not set per disk. The compression option is currently set to: Compression options available to User Shares. To set compression per disk, change your selection under the Compression options available to... setting under Settings-->Disk Settings.
User share ebooks compression=yes
User share familydocs compression=yes
User share comics compression=no
User share HEVC compression=no
If possible, it may be wise to allow exclusively setting compression at the user level or at the disk level, where setting one disables the other, to avoid contested settings. IMHO setting them at the share level adds complexity, but I would hope to reduce unnecessary compute.
I'm very new to the concept, just trying to save space on a lot of compressible data, with a fair amount of data I can't compress in the wings, and I know for me, at least, it would seem to help.