I have turned on Smart Sync on my laptop and I'm impressed how much space it saves!
However, here's something that happens repeatedly: I have a folder that contains a lot of audio files. There's two subfolders that I am using currently, adding and editing files, the rest is archival stuff (about 100 files) that I don't need currently. However, as soon as I start working in the subfolders, Dropbox starts downloading other files on the top level of this folder, even though they are marked as "online only." That uses up bandwidth and disk space. I can stop every download individually – but is there something else I can do about it?
However, as soon as I start working in the subfolders, Dropbox starts downloading other files on the top level of this folder, even though they are marked as "online only."
Something on your computer is trying to access the files.
Any process on your computer that tries to access a file will cause Dropbox to download the file back to your computer and mark it as local again. This could happen from a backup process, virus scan, even just browsing a folder with previews enabled. If something tries to access a file, Dropbox is told to download it again.
Could just having a Finder window of a folder with these files in it be a reason to start downloading? That would defeat the purpose of Smart Sync - I want to see what’s I. The folder without actually downloading it.