Moving Plex & Transmission to a second Synology volume

Adding a new drive to a Synology NAS and switching Transmission downloads and Plex libraries over to the new volume.

The goal

My first volume was 90% full, so I added a new drive as a second storage pool (Volume2). Everything new should now download to and live on Volume 2.

This builds on my earlier setup in Plex & Transmission on a Synology NAS, where Transmission runs in Portainer and its folders are mapped to /volume1.

The important part is that both the in-progress and the finished downloads are on the same volume. Transmission writes to a temporary incomplete folder and moves each file when it finishes. On the same volume that move is an instant rename. Across volumes, every file is copied in full.

Create the shared folder on Volume 2

In DSM go to Control Panel → Shared Folder → Create and set the location to Volume 2.

Synology won't allow two shared folders with the same name, even on different volumes, so I couldn't reuse Media. I called it Media2.

Inside it, in File Station, create plain folders (Create → Create folder, not shared folders):

Media2              (shared folder)
├── downloads
│   └── incomplete
├── movies
└── tv

I used short lowercase names, which keeps the mappings simple and avoids the space in TV Series. Synology paths are case-sensitive, so the names must match the Portainer mappings exactly.

Transmission will create incomplete itself if it's missing, but creating it up front makes sure it has the shared folder's permissions.

Recycle bin

DSM turns on the Recycle Bin by default for new shared folders, so a #recycle folder appears in Media2. To match my Volume 1 share I turned it off in Shared Folder → Media2 → Edit → General → Enable Recycle Bin, then deleted the folder.

If you keep it on, deleted media keeps using space until the bin is emptied, so set an emptying schedule.

Permissions

In Shared Folder → Media2 → Edit → Permissions, match whatever the original Media share has. For me that was:

my own user: Read/Write
plex: Read/Write
guest: No Access

The catch with Plex on DSM 7: the Plex package runs as a hidden system account, not the plex user. Without it, Plex could see Media2 but the folder appeared empty when browsing.

To fix it:

Change the dropdown at the top of the permissions screen from Local users to System internal user.
Give PlexMediaServer Read/Write. On my original share this showed as "Custom", which is just Plex's installer setting detailed rules.
Restart Plex in Package Center → Plex Media Server → Stop, then Run.

Update the Transmission stack

I'd already removed all the old torrents, so nothing was seeding from Volume 1. That meant I could point the original container paths (/downloads, /movies, /tv) at Volume 2 and keep using the same paths as before.

In Portainer (usually http://nas:9000), go to Stacks, click the transmission link (the checkbox only selects stacks to remove), then open the Editor tab.

services:
  transmission:
    container_name: Transmission
    image: ghcr.io/linuxserver/transmission:4.0.5
    mem_limit: 4g
    cpu_shares: 768
    security_opt:
      - no-new-privileges:true
    restart: on-failure:5
    ports:
      - 9091:9091
      - 51413:51413/udp
      - 51413:51413
    volumes:
      - /volume1/docker/transmission/data:/config:rw
      - /volume1/docker/transmission/watch:/watch:rw
      - /volume2/Media2/downloads:/downloads:rw
      - /volume2/Media2/movies:/movies:rw
      - /volume2/Media2/tv:/tv:rw
    environment:
     USER: chris
     PASS: ********
     TZ: Europe/Paris
     PUID: 1026
     PGID: 100

The config and watch mappings stay on Volume 1. They only hold Transmission's settings and small .torrent files, and moving them would reset the Transmission setup.

Click Update the stack. If it offers to re-pull the image, leave that off, because the image is pinned to 4.0.5.

The old /volume1/docker/transmission/downloads folder is no longer used and can be deleted once it's empty.

Check Transmission's settings

Open http://nas:9091/ and go to Preferences:

Download to: /downloads
Use temporary folder: ticked, set to /downloads/incomplete

Torrents are added the same way as before, for example /tv/Ridley/Season 2 or /movies. They now land in Media2 on Volume 2.

Add the new folders to Plex

Add the new folders to the existing libraries rather than creating new ones. A single Plex library can draw from several folders, so content from both volumes appears together.

Open Plex at http://nas:32400/web.
Go to Settings → Manage → Libraries.
Edit the TV library, open Add folders, browse to volume2 → Media2 → tv and save.
Do the same for the Movies library with volume2 → Media2 → movies.
Run ⋯ → Scan Library Files on each library.

Keep the Volume 1 folders in each library, because the existing media still lives there. A new season of an existing show can go to /tv/ShowName/Season X on Volume 2 and Plex merges it with the earlier seasons.

Testing it

Add a small torrent and check in File Station that:

the partial file appears in Media2/downloads/incomplete while it downloads
it moves into movies or tv almost instantly when it finishes
it shows up in Plex after a library scan