Copy from Mac SSD to NAS results in error since upgrading to Tahoe - Updates

It's not a Tahoe problem. I get the same problem on Sequoia when copying to my QNAP NAS. Not only does it create a load of _DS files it creates small _*** files for every file that's copied. E.g. if I copy a seeds.doc file to my NAS it will create a _seeds.doc file which is a small file. This happens with Finder and rsync and, hence, any apps that use rsync such as Carbon Copy Cloner.

Only Finder has a problem with the NAS when these _*** files are in the directory and note that Finder doesn't display them even if display hidden is toggled. I see them when I log in to the NAS web interface and use the NAS File Manager, which doesn't have a problem with them. They seem to lock some file for Finder but not the QNAP file manager.

I believe they are something to do with SMB. I'm on NAS, you're on Synology and we both see it so unfortunately that implies it's a MacOS problem.

You can delete all the _*** files using a Terminal command, although they will be recreated the next time you copy. When I dug into this I noticed that Carbon Copy Cloner was just adding copies of the same file with random characters in the name, so it's clearly impacted by it. i.e. i'd see Seeds.doc Seeds.doc.dje, Seeds.doc.tjd, Seeds.doc.etc. They were all updated files but CCC was obviously not able to overwrite the original file.

dot_clean -m --keep=native /Volumes/<insert your NAS details>

You can just type "dot_clean -m --keep=native " and then drag the relevant directory from you NAS onto terminal. However, they will come back the next time you add files to the NAS from Mac. I run it before a CCC backup to make sure that I'm not just adding files instead of overwriting. I've left my Time Machine backup alone but I'm a bit worried about it.

I spent a bit of time on this when I first saw it last year, including changing the SMB settings on Mac to not write the _*** files but nothing fixed it and it's way outside my area of expertise. I've tested my Time Machine backups to make sure they are not being buggered but I have a niggling worry about this and will give it more time when I can.

Filet-o-Fish wrote:

Can't format a Synology NAS as Mac format. All sorts of reasons why that isn't a great idea for us. But mostly it worked fine before Tahoe and now...not fine. 🤷‍♂️

It worked for you before Tahoe. There are many reports of this issue going back decades. I don’t know what causes it to start stumbling, but it has for a very long time. Clearing the metadata with dot_clean may be your only option. I would also imagine you may be able to prevent writing those files on the server configuration.

it creates small _*** files for every file that's copied.

That means the drive format is not capable of storing metadata with the file. Format the NAS drive to be an Apple format such as APFS or HFS+, or a format that supports embedded metadata (Apple Double). There was an app that would prevent this (I think), but I don’t know if it still works, BlueHarvest.

When you copy to a volume that doesn’t support metadata, the metadata is stripped off the file and written to the ._ files. If you copy the file back, the metadata is merged back into the file.

That might explain this from filet-o-fish:

No idea why our system is different from everyone else's. Neither does Apple or Synology.

Create a macOS writable sparse disk image. Mount the disk image and copy your files to the disk image.

I'm going to play with this a bit next week. I'll switch back to AFP (not available with Tahoe, but I'm still on Sequoia) and see if it still happens and then I'll tinker with the NAS settings. I'll also see if it's possible to put a Sparsebundle on the NAS. Assuming I don't get sidetracked I'll post back if anything interesting turns up.

It's a four-bay SOHO NAS from QNAP. I get no choice on the format of the drive. I assume the OP is in the same situation.