Issue with docker(?) and a mergerfs disk

[p3lim]

General description

I noticed while installing ruTorrent through Docker that I any torrent I added was not processing (downloading). After a while I found out (with the assistance of the linuxserver.io community on discord) that it seemed to be mergerfs' fault.
While I have mapped the docker volume to /mnt/storage (a mergerfs disk), the download didn't process, but mapping it directly to a disk (e.g. /mnt/disk2/downloads) it worked flawlessly.

Expected behavior

Just work™ (it should download without any issue)

Actual behavior

Download doesn't work, had to map it directly to a disk.

Precise steps to reproduce the behavior

1. Install Debian, mergerfs, docker
2. Set up disks as per config below
3. Install ruTorrent through docker

• docker run -v /mnt/storage/downloads:/downloads -e PGID=1001 -e PUID=1001 -p 8080:80 linuxserver/rutorrent
• PGID and PUID is a dedicated user, which is the owner of the mounts + mergerfs volume (chown <user> /mnt/storage)

4. Visit rutorrent (<your-ip>:8080)
5. Add a torrent

At this point, the torrent won't process while the docker volume is mapped to a mergerfs disk, while directly to a disk works fine.

System information

Please provide as much of the following information as possible:

• mergerfs version: mergerfs -V

mergerfs version: 2.18.0
FUSE library version: 2.9.7
fusermount version: 2.9.7
using FUSE kernel interface version 7.19

• mergerfs settings: cat /etc/fstab or the command line arguments

/dev/disk/by-id/ata-WDC_WD40EFRX-...-part1  /mnt/disk1      xfs     defaults        0 0
/dev/disk/by-id/ata-WDC_WD40EFRX-...-part1  /mnt/disk2      xfs     defaults        0 0
/dev/disk/by-id/ata-WDC_WD40EFRX-...-part1  /mnt/disk3      xfs     defaults        0 0
/mnt/disk*      /mnt/storage    fuse.mergerfs   direct_io,defaults,allow_other,minfreespace=50G,fsname=mergerfs 0 0

• Linux version: uname -a

Distributor ID: Debian
Description:    Debian GNU/Linux 9.3 (stretch)
Release:        9.3
Codename:       stretch

Linux debian 4.9.0-4-amd64 #1 SMP Debian 4.9.65-3+deb9u1 (2017-12-23) x86_64 GNU/Linux

• Versions of any additional software being used

- rtorrent client version 0.9.6.
- ruTorrent 3.8
- Docker version 18.01.0-ce, build 03596f5

• List of drives, filesystems, & sizes: df -h

Filesystem      Size  Used Avail Use% Mounted on
udev            7.9G     0  7.9G   0% /dev
tmpfs           1.6G  9.7M  1.6G   1% /run
/dev/sda2       148G  2.9G  138G   3% /
tmpfs           7.9G     0  7.9G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           7.9G     0  7.9G   0% /sys/fs/cgroup
mergerfs         12T  3.1T  8.1T  28% /mnt/storage
/dev/sda1       511M   27M  485M   6% /boot/efi
/dev/sde1       3.7T  2.4T  1.3T  66% /mnt/disk3
/dev/sdb1       3.7T  571G  3.1T  16% /mnt/disk2
/dev/sdd1       3.7T   89G  3.6T   3% /mnt/disk1
tmpfs           1.6G     0  1.6G   0% /run/user/1000

• strace of mergerfs while app tried to do it's thing: strace -f -p <mergerfsPID> -o /tmp/mergerfs.strace.txt
  https://gist.github.com/p3lim/9220d8ad3d295b0262c52f677a200134

[p3lim]

I could probably help nail it down even further if the logs don't stand out.

[trapexit]

rtorrent doesn't work with the direct_io flag. It's documented in the tips / notes section https://github.com/trapexit/mergerfs#tips--notes

[p3lim]

Thanks for the quick reply, after reading the tips I've decided to mount mergerfs twice (one with direct_io and one with dropcacheonclose=true).
Has there been any benchmarking to see the difference between those two options? Would love to see.

Edit: Getting fuse: unknown option 'dropcacheonclose=true' when mounting.

# mergerfs
/mnt/disk*      /mnt/storage    fuse.mergerfs   direct_io,defaults,allow_other,minfreespace=50G,fsname=mergerfs 0 0
# another one for special cases where mmap is used (rtorrent)
/mnt/disk*      /mnt/storage_cached     fuse.mergerfs   dropcacheonclose=true,defaults,allow_other,minfreespace=50G,fsname=mergerfs     0 0

[trapexit]

Benchmarks in my experience are somewhat useless given the number of permutations of hardware and software. Always best to run tests yourself and there are some simple examples to do so in the docs.

As for the unknown option... you're using an old version. Install the latest from the releases github page.

[p3lim]

That solved it, thank you so much for the assistance, and for making this tool in the first place.

[trapexit]

No problem.

[nullredvector]

thank you for this thread! had the same problem!

[trapexit]

It's mentioned twice in the docs. Just search rtorrent.

https://github.com/trapexit/mergerfs#tips--notes

[nullredvector]

ahh google landed me here way before i thought to check the docs :D

[nation-wide]

Holy **** I almost lost my mind with this issue. Should've looked at mergerfs doc earlier. Thanks for the awesome software.

[DebtFromAbove]

Same problem with influxdb. Glad I came across this issue