Rsync doesn't handle time correctly on a mounted folder on MacOS

Question

I have a mounted a folder from my NAS with mount -t smbfs -o -d=755,-f=755 //nas.local/backup ~/backup.

I now try to rsync a local folder to this distant folder with something like rsync --modify-window=30 -irvt --info=progress2 --delete-after test-dir ~/backup.

I've tried a lot of rsync options, but I'm always getting >f..t....... on all the files, so I always have speedup is 1.00 even if I run the same rsync multiple times in the row, without changing anything in the source folder. I don't have this issue when running the rsync between 2 local folders.

What am I doing wrong here ?

Thanks,

Answer 1

If your NAS allows ssh login you will generally get a significantly more efficient file transfer if you ignore the SMB share and have rsync talk to the NAS directly:

rsync -rtiv --info=progress2 --delete test-dir remoteUser@nas:~/backup

Otherwise, remove the --modify-window=30 and try the copy again:

rsync -rtiv --info=progress2 --delete test-dir ~/backup

For either suggestion you should to ensure the local and remote systems use the same time source so that they have the same date/time. NTP can be a good choice for Internet-connected systems.

If you are writing to a FAT filesystem you will need to provide --modify-window=1 to overcome the limitation of having only 2-second granularity in the filesystem metadata. (I know of no system where timestamps are accurate only to the nearest minute; MacOS APFS itself is accurate to the nanosecond. It doesn't mean there aren't any, but requiring --modify-window=30 seems exceedingly unlikely unless you're trying to work around a completely different issue.)