I just got a new iPhone 8. I switched over from backing up my phone on my computer to iCloud, but I left it all night to back up and it never completed. I’m not sure if that’s a problem or not?
iPhone 8 Plus, iOS 11.2.6
The short answer is that it would depend on the speed of your WI-FI connection. The initial backup can be several GB in size. Once the initial backup is completed, iCloud backups are incremental thereafter and usually in the order of tens or hundreds of MBs. You may want to perform the initial backup manually when you have a fast WI-FI connection:
iCloud: Back up your iOS device to iCloud
You may also want to first check how much iCloud storage you have available (and possibly clean it). See the "Make more space available in iCloud" section in:
How long should it take the first time to fully back up?
