Some questions regarding MergerFS

Think of mergerfs as a mounted folder on the system independently of the disks (a mount on linux translates to an actual folder on the system). All mergerfs does is write the files to the mounts of the disks that make up the pool according to the policy you have chosen.

So, if your group is three disks for example, in the system you would have:

(Note: These paths are dummy for the example, actually they are something like /srv/srv/dev-disk-by-uuid-0aa5667d-ec21-4d5c-b168-1e6c137e4a62)

/Disk1

/Disk2

/Disk3

/mergerfs

The mergerfs mount, you'll find it if you look in /srv along with the other mounts. What mergerfs does is show this folder to OMV as a mix of everything on the other three disks. But what you see there is not real. The files are actually on each drive. In the path of each disk you can see the files it contains.

From here answering your questions is easy:

(1) Suppose you want to move data from /Disk1 to /Disk2. Just move them as you normally would if there were no mergers. Use the mount paths /Disk1 and /Disk2.

(2) In this document you should find the way to remove a disk from the pool. https://wiki.omv-extras.org/do…mv6:omv6_plugins:mergerfs I have not read it completely, if the procedure is not there, post it again here.

(3) Depends on the policy you have chosen

(4) Create that directory in the disk path instead of in the pool.

(5) Depends on the policy you have chosen. mergerfs could create that folder automatically on another disk or force you to do it manually.

Quote from tsch

So adding an additional Share for every hdd of the MergerFS-pool should enable me to copy files between desired hdds including adding directories where I want them to be added.

Yes.

But keep in mind that if you copy a file to two disks in the same pool, mergerfs will see the duplicate file, since that file exists twice within the pool. What is the objective of this? If it is simply to remove a disk from the pool, you can remove this disk previously. You can then copy the files back into the pool and mergerfs will redistribute them to the remaining disks according to the chosen policy.

Quote from tsch

There's something I'm doing wrong. I've shared all 3 hdds but can't see them on my Win-client.

I can access the MergerFS-pool though but the three new Shares are not displayed on the client.

I've just reproduced this in a virtual machine, just in case it changed the behavior of the plugin. I have not had any problems doing it, it has worked as expected.

A mergerfs pool with three disks. Shared folder created in the pool. Shared folder created on disk1. Both folders shared with the samba service. Both are accessible from Windows and can be written to. Files in the disk1 folder end up being written to disk1.

Quote from tsch

but I can't find these directories on none of the dedicated hdds

What tool are you looking for those folders with?

Quote from tsch

I've mounted the three Shared hdds on my Windows-client and I can't see any directory or file.

You have made some configuration error. Review the paths of the disks and folders created. WinSCP is very useful for clearly seeing the structure of the mounts.

Quote from chente

What is the objective of this? If it is simply to remove a disk from the pool,...

You haven't answered me on this. Is that what you want to do?

The behavior depends on the policy you choose.

For example:

If you choose more free space if the path exists. The files will go to the disk that has the folder created, that is, they will only be written to one disk.

If you choose more free space. The path will be created on all disks and the files will be spread equally.

Here you have all the policies that you can configure. https://github.com/trapexit/mergerfs#policy-descriptions

Samba has nothing to do with all this, it's just a folder sharing service.

Quote from gderf

LFS is my use case policy and there is no "spread equally" behavior. Writes are to the disk with the least free space until it is filled.

You are right, I was wrong. I was thinking more free space and wrote lower free space

Edited, thanks.

Quote from tsch

How can I delete the pool in OMV?

That's because that group is referenced with some services. It can be samba, rsync, etc.

To remove it, you must first remove all services pointing to that file system, including shared folders, etc.

Optionally, if you don't want to remove those folders, you can temporarily redirect them by editing their relative path to point to an empty folder on another drive. This will also divert all services to the new route.

When you're done redoing your mergerfs pool, edit the relative paths again to point to the new pool and everything will be back to normal.

If you have correctly configured the user and access permissions you should be able to access all of them.

It strikes me that you are guided by /sda1 /sdb1 etc. You shouldn't, those names can change on any reboot, that's why UUIDs are used, they are invariant. Maybe that's where the error comes from. When you create the d1 shared folder you must do it in the UUID corresponding to that disk.

Are you doing it like this?