Plex: Adding an expansion unit to a Synology NAS for additional media storage.
This covers an expansion unit being added for both a package and docker container install of Plex server.
Three options...
Move a large TV Show library to a new volume to gain additional space on the original volume.
Leave all existing Plex media on the original volume and use the new volume for new Plex media of all types.
Expand your existing volume to the expansion unit, which I would only recommend if you are already using SHR2 as your RAID configuration.
With a volume made up of 9 or 10 drives, I prefer the two drive fault tolerance of SHR2, over the one drive fault tolerance of SHR, no matter if it's a large capacity Synology model or a 5 bay plus model with an expansion unit attached.
If you could add 30 or 40 drives to one Synology NAS through multiple expansion units, I'd also want a SHR3 option to magically appear.