Union Filesystems crashes - "Transport endpoint is not connected"

Hello again!

I am trying to set up a datapool for my two SD cards with Union Filesystems, but the plugin crashes every time I am trying to transfer data to the pool. The SD cards are connected via two different USB-ports on my Rock64. In the future, the two SD cards are going to be replaced with two HDDs, but in the meanwhile I am just playing around.

This is what I do:
- Mount the to SD cards --> named "ALPHA" & "BRAVO"
- Create a pool with the UnionFS plugin (version 4.0.2) (Create policy: Most free space.) --> named "DATAPOOL"
- Create a shared folder connected to the pool --> named "ALLDISKS"
- Give user1 read/write-permissions to "ALLDISKS"
- Share the folder "ALLDISKS" with Samba
- Trying to transfer some data to the shared folder via my Windows computer
- This error shows up in the WebGUI:

Error #0:
OMV\ExecException: Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C.UTF-8; df -PT '/srv/fb97e7c0-e130-4e4d-b1df-33cac946b547' 2>&1' with exit code '1': df: /srv/fb97e7c0-e130-4e4d-b1df-33cac946b547: Transport endpoint is not connected in /usr/share/php/openmediavault/system/process.inc:182
Stack trace:
#0 /usr/share/php/openmediavault/system/filesystem/union.inc(258): OMV\System\Process->execute(Array)
#1 /usr/share/openmediavault/engined/rpc/filesystemmgmt.inc(157): OMV\System\Filesystem\Union->getStatistics()
#2 /usr/share/php/openmediavault/rpc/serviceabstract.inc(612): OMVRpcServiceFileSystemMgmt->{closure}()
#3 /usr/share/openmediavault/engined/rpc/filesystemmgmt.inc(172): OMV\Rpc\ServiceAbstract->asyncProc(Object(Closure))
#4 [internal function]: OMVRpcServiceFileSystemMgmt->enumerateFilesystems(NULL, Array)
#5 /usr/share/php/openmediavault/rpc/serviceabstract.inc(123): call_user_func_array(Array, Array)
#6 /usr/share/openmediavault/engined/rpc/filesystemmgmt.inc(320): OMV\Rpc\ServiceAbstract->callMethod('enumerateFilesy...', NULL, Array)
#7 [internal function]: OMVRpcServiceFileSystemMgmt->getList(Array, Array)
#8 /usr/share/php/openmediavault/rpc/serviceabstract.inc(123): call_user_func_array(Array, Array)
#9 /usr/share/php/openmediavault/rpc/serviceabstract.inc(149): OMV\Rpc\ServiceAbstract->callMethod('getList', Array, Array)
#10 /usr/share/php/openmediavault/rpc/serviceabstract.inc(565): OMV\Rpc\ServiceAbstract->OMV\Rpc\{closure}('/tmp/bgstatusUX...', '/tmp/bgoutput2h...')
#11 /usr/share/php/openmediavault/rpc/serviceabstract.inc(159): OMV\Rpc\ServiceAbstract->execBgProc(Object(Closure))
#12 /usr/share/openmediavault/engined/rpc/filesystemmgmt.inc(470): OMV\Rpc\ServiceAbstract->callMethodBg('getList', Array, Array)
#13 [internal function]: OMVRpcServiceFileSystemMgmt->getListBg(Array, Array)
#14 /usr/share/php/openmediavault/rpc/serviceabstract.inc(123): call_user_func_array(Array, Array)
#15 /usr/share/php/openmediavault/rpc/rpc.inc(86): OMV\Rpc\ServiceAbstract->callMethod('getListBg', Array, Array)
#16 /usr/sbin/omv-engined(537): OMV\Rpc\Rpc::call('FileSystemMgmt', 'getListBg', Array, Array, 1)
#17 {main}

Does anyone know if there are known bugs with the plugin? Should I try an older version of the plugin?

Additional information
- The OMV image is downloaded from https://github.com/ayufan-rock64/linux-build/releases/ (version 0.9.14: gitlab-ci-linux-build-159)
- I have not tried with any other images yet

I hope someone can help me with the problem

Best regards
Marius

Quote from ryecoaaron

OMV version?
SD card filesystem?

OMV version is 4.1.27-1 (Arrakis) - see the attachment.
SD card filesystem is EXT4.

Quote from ryecoaaron

What is the output of: dpkg -l | grep mergerfs
grep 33cac946b547 /proc/mounts

Thank you for helping!

This is the output:

root@rock64:~# dpkg -l | grep mergerfs
ii  mergerfs                                                        2.28.2~debia                                                                                                         n-stretch                    armhf        another FUSE union filesystem

root@rock64:~# grep 33cac946b547 /proc/mounts
ALPHA:BRAVO /srv/fb97e7c0-e130-4e4d-b1df-33cac946b547 fuse.mergerfs rw,relatime,                                                                                                         user_id=0,group_id=0,default_permissions,allow_other 0 0

Quote from ryecoaaron

Not seeing anything wrong yet. What about grep mergerfs /etc/fstab

Hm... Do you know any bugs with the plugin?

Output of the command is:

root@rock64:~# grep mergerfs /etc/fstab
/srv/dev-disk-by-label-ALPHA:/srv/dev-disk-by-label-BRAVO /srv/6ae2eee8-f0ff-4f8b-848e-a35cfb5870c6 fuse.mergerfs defaults,allow_other,direct_io,use_ino,category.create=mfs,minfreespace=4G 0 0

Quote from ryecoaaron

This seems like a potential mergerfs issue. Maybe @trapexit (author of mergerfs) would have an idea?

It's worth a try. Thank you!

I came over this, which led me to this and this. The armhf versions here are libfuse2_2.9.9-2 and fuse_2.9.9-2. The output of mergerfs -v on my system is:

root@rock64:~# mergerfs -v
mergerfs version: 2.28.2
FUSE library version: 2.9.7-mergerfs_2.28.0
fusermount version: 2.9.7
using FUSE kernel interface version 7.29

The versions are newer than 2.9.4 (which was recommended here), but it's not the latest release(?)

Quote from ryecoaaron

mergerfs has its own fuse libraries compiled in. So, the system fuse libraries shouldn't matter.

Ah, I understand...
Well, I guess I have to wait for the author, @trapexit, as you recommended That said, I have seen several post on the forum describing the exact same problem, but it looks like it never was solved. I hope I will be the lucky man! Anyway, thank you so far!

@ryecoaaron
By the way;
Are there any UnionFS-like OMV-supported plugins/dockers I can use instead? This current NAS build is only for testing, so if there are any, I may want to try them until my current problem is solved.

Quote from trapexit

I can't comment without details. What mergerfs version? Is it up to date? Can you reproduce it outside OMV?

Look at this:

Quote from Mumbedeus

Code

root@rock64:~# mergerfs -v
mergerfs version: 2.28.2
FUSE library version: 2.9.7-mergerfs_2.28.0
fusermount version: 2.9.7
using FUSE kernel interface version 7.29

The versions are newer than 2.9.4 (which was recommended here), but it's not the latest release(?)

What do you mean by "Can you reproduce it outside OMV?"?

Quote from trapexit

I really can't comment without the ability to reproduce it. There are lots of reasons why it could have died. Have you tried running mergerfs on the commandline in the foreground to see what the output might be as it dies? Or ... journald logs or something?

No, I have not tried that as I am not that kind of an expert with Linux. Would you mind guiding me, or maybe link to a webpage showing how to do it?
Currently everyting is set up from the WebGUI in OMV. When trying to add a folder from my PC with Samba, the pool crashes.

Quote from trapexit

On a different system. I don't use OMV. I don't have a ROCK64 board.

I can't, but what I can do is try to set it up on a ROCKPro64 board. Only problem is that this board haven't arrived at my place yet (ordred a few days ago)...