What are the pros and cons of using Named vs Anonymous volumes in Docker for self-hosting?

I’ve always used “regular” Anonymous volumes, and that’s what is usually in official docker-compose.yml examples for various apps:

volumes:
  - ./myAppDataFolder:/data

where myAppDataFolder/ is in the same folder as the docker-compose.yml file.

As a self-hoster I find this neat and tidy; my docker folder has a subfolder for each app. Each app folder has a docker-compose.yml, .env and one or more data-folders. I version-control the compose files, and back up the data folders.

However some apps have docker-compose.yml examples using named volumes:

services:
  mealie:
    volumes:
      - mealie-data:/app/data/
volumes:
  mealie-data:

I had to google documentation https://docs.docker.com/engine/storage/volumes/ to find that the volume is actually called mealie_mealie-data

$ docker volume ls
DRIVER    VOLUME NAME
...
local     mealie_mealie-data

and it is stored in /var/lib/docker/volumes/mealie_mealie-data/_data

$ docker volume inspect mealie_mealie-data
...
  "Mountpoint": "/var/lib/docker/volumes/mealie_mealie-data/_data",
...

I tried googling the why of named volumes, but most answers were talking about things that sounded very enterprise’y, docker swarms, and how all state information should be stored in “the database” so you shouldnt need to ever touch the actual files backing the volume for any container.

So to summarize: Named volumes, why? Or why not? What are your preferences? Given the context that we are self-hosting, and not running huge enterprise clusters.

  • vegetaaaaaaa@lemmy.worldEnglish
    5·
    3 days ago
    • step 1: use named volumes
    • step 2: stop your containers or just wait for them to crash/stop unnoticed for some reason
    • step 3: run docker system prune --all as one should do periodically to clean up the garbage docker leaves on your system. Lose all your data (this will delete even named volumes if they are not in use by a running container)
    • step 4: never use named or anonymous volumes again, use bind mounts

    The fact that you absolutely need to run docker system prune --all regularly to get rid of GBs of unused layers, test containers, etc, combined with the fact that it deletes explicitely named volumes makes them too unsafe for my taste. Just use bind mounts.

    • sugar_in_your_tea@sh.itjust.worksEnglish
      3·
      2 days ago

      I also like browsing folders of data, which makes backups easy. I only use volumes for sharing incidental data between containers (e.g. certificates before I switched to Caddy, or build pipelines for my coding projects).

      Use volumes if you don’t care about the data long term, but you may need to share it with other containers. Otherwise, or if in doubt, use bind mounts.

  • ikidd@lemmy.world
    5·
    4 days ago

    I like having everything to do with a container in one folder, so I use ./ the bind mounts. Then I don’t have to go hunting all over hells half acre for the various mounts that docker makes. If I backup/restore a folder, I know I have everything to do with that stack right there.

    • klangcola@reddthat.comOPEnglish
      1·
      3 days ago

      This has been my thinking too.

      Though after reading mbirth’s comment I realised it’s possible to use named volumes and explicitly tell it where on disk to store the volume:

          volumes:
      - my-named-volume:/data/
volumes:
  my-named-volume:
    driver: local
    driver_opts:
      type: none
      device: "./folder-next-to-compose-yml"
      # device: "/path/to/well/known/folder"
      o: bind

      It’s a bit verbose, but at least I know which folder and partition holds the data, while keeping the benefits of named volumes.

      • ikidd@lemmy.world
        1·
        3 days ago

        I guess on the rare occasions you need to specify the driver, this is the answer. Otherwise, it’s a lot of extra work for no real benefit.

  • Semi-Hemi-Lemmygod@lemmy.worldEnglish
    1·
    4 days ago

    Named volumes let you specify more details like the type of driver to use.

    For example, say you wanted to store your data in Minio, which is like S3, rather than on the local file system. You’d make a named volume and use the s3 driver.

    Plus it helps with cross-container stuff. Like if you wanted sabnzbd and sonarr and radarr to use the same directory you just need to specify it once.

    • mbirth@lemmy.mlEnglish
      1·
      4 days ago

      Or just something as simple as using a SMB/CIFS share for your data. Instead of mounting the share before running your container, you can make Docker do it by specifying it like this:

      services:
  my-service:
    ...
    volumes:
      - my-smb-share:/data:rw

volumes:
  my-smb-share:
    driver_opts:
      type: "smb3"
      device: "//mynas/share"
      o: "rw,vers=3.1.1,addr=192.168.1.20,username=mbirth,password=supersecret,cache=loose,iocharset=utf8,noperm,hard"

      For type you can use anything you have a mount.<type> tool available, e.g. on my Raspberry this would be:

      $ ls /usr/sbin/mount.*
/usr/sbin/mount.cifs*  /usr/sbin/mount.fuse3*       /usr/sbin/mount.nilfs2*  /usr/sbin/mount.ntfs-3g@  /usr/sbin/mount.ubifs*
/usr/sbin/mount.fuse@  /usr/sbin/mount.lowntfs-3g@  /usr/sbin/mount.ntfs@    /usr/sbin/mount.smb3@

      And the o parameter is everything you would put as options to the mount command (e.g. in the 4th column in /etc/fstab). In the case of smb3, you can run mount.smb3 --help to see a list of available options.

      Doing it this way, Docker will make sure the share is mounted before running the container. Also, if you move the compose file to a different host, it’ll just work if the share is reachable from that new location.

  • irotsoma@lemmy.blahaj.zoneEnglish
    0·
    4 days ago

    I use NFS shares for all of my volumes so they’re more portable for future expansion and easier to back up. It uses additional disk space for the cache of course, but i have plenty.

    When I add a second server or add a dedicated storage device as I expand, it has made it easier to move with almost no effort.

    • klangcola@reddthat.comOPEnglish
      0·
      3 days ago

      How does this work? Where is additional space used for cache, server or client?

      Or are you saying everything is on one host at the moment, and you use NFS from the host to the docker container (on the same host)?

      • irotsoma@lemmy.blahaj.zoneEnglish
        2·
        2 days ago

        Yeah, the system was on a single server at first and eventually expanded to either a docker swarm or Kubernetes cluster. So the single server acts as both a docker host and an NFS server.

        I’ve had this happen multiple times, so I use this pattern by default. Mostly these are volumes with just config files and other small stuff that it’s OK if it’s duplicated in the docker cache. If it is something like large image caches or videos or other volumes that I know will end up very large then I probably would have started with storage off the server in the beginning. It saves a significant amount of time to not have to reconfigure everything as it expands if I just have a template that I use from the start.