Open Radar

 
Summary
By default, many common applications store large and unwieldy or machine-specific files in the ~/Documents/ directory on OS X. The most glaring example that I've encountered is Parallels. When you create a VM in Parallels, it typically saves the .pvm bundle (containing metadata, disk images and snapshot data) in ~/Documents/Parallels/.

After enabling iCloud Drive Documents and Desktop sharing, the system began trying to upload the VMs on my machine. This was not at all obvious until I noticed the iCloud Drive upload pie chart was not visibly progressing. Opening the progress pane showed that there were nearly a hundred GB to be uploaded, and then simple investigation of the Documents folder revealed that the Parallels folder was being synced with everything else.

Clearly this sequence of events could cause a great deal of user confusion when their iCloud Drive fills up or the disks of other Macs that are set to also share Documents and Desktop are suddenly consumed by large synced files. I wonder now if the presence of so many large files is why the iCloud system preferences pane prompted me to upgrade my storage (with no explanation as to why) when I enabled iCloud Drive.

Please consider adding warnings when enabling Documents and Desktop in iCloud Drive for users who have large or known inappropriate file types in those directories. Please also consider adding an option for exclusion of either uploading or downloading of specific files. Remember that until now, the Documents and Desktop folders were "safe" to fill up with hundreds of gigabytes of VMs, git repositories, database files, disk images, and other things that you typically don't want naively synchronized across machines.