Symlinked MobileSync folder but still "not enough free space"

I have an external hard drive and I plan to put iPhone backups on it.

I did symlink to it this way:

ln -s /Volumes/external/Backup ~/Library/Application Support/MobileSync

When I'm trying to do a backup of my iPhone normally from iTunes, I get an error:

However my drive has 1 TB of free space. What's wrong?


iTunes doesn't know you've symlinked the MobileSync folder, so still checks the normal disk for its free space. Make sure there's enough free space on the disk containing your home folder, even though that space won't be consumed because of the symlink.