I made the mistake to get a 16Gb iPhone and now I'm running out of space pretty much all the time. If I'm trying to do a WhatsApp backup it tells me that I need 3 GB of storage. It isn't at all clear where this backup will live.
If I clear that much space, and do the backup to iCloud, will this permanently take up 3 GB on my phone's internal storage or will it just be in the iCloud?