How to Prevent Data Transfer When Moving Folders Within the Same Location?

[8ullyMaguire]

When moving folders within my MergerFS pool via a graphical file manager, I've noticed that sometimes the operation triggers a data transfer between drives—even if I'm simply moving a folder into a subfolder in the same directory tree. For large folders, this can be extremely slow and isn't the outcome I'm hoping for.

Questions

• What operation is actually being performed at the filesystem level during these "move" actions?
• What MergerFS policies or configuration options can I use to ensure that moving a folder within the same branch keeps all files on the original drive, avoiding unnecessary data copying?

I'm guessing the action it's performing is something like rename or link, and the configuration I'm missing is something like either func.rename=epall or func.link=epall. Would this configuration be the same as ignorepponrename=true?

[trapexit]

• https://trapexit.github.io/mergerfs/config/functions_categories_policies/#policy-descriptions
• https://trapexit.github.io/mergerfs/config/rename_and_link/

It's all described in the documentation.

If you don't want mergerfs to only consider branches with paths which already exist then change the create policy to one you want. There is very little reason for people to use ep policies.

What operation is actually being performed at the filesystem level during these "move" actions?

• https://trapexit.github.io/mergerfs/faq/technical_behavior_and_limitations/#how-does-mergerfs-handle-moving-and-copying-of-files

What MergerFS policies or configuration options can I use to ensure that moving a folder within the same branch keeps all files on the original drive, avoiding unnecessary data copying?

There is no such thing as "moving a folder within the same branch". You link, rename, create, etc. in the filesystem and then the policies decide what happens where. There is no context besides what mergerfs can infer from the request otherwise. If the request is rename(src,dst) and you told it to only consider branches with the relevant paths then that's what it does. if src and dst parent paths don't both exist on the same branch then that is an error. The software in question might not even be trying to rename directories. It might be working only at the file level.

The first question is why do you want to restrict location of files?