performance - Windows Update showed "Downloading updates 95%" for hours

I was using Windows 10 Home, version 1607 (OS build 14393.693).

The computer was a bit slow earlier today. Task Manager indicated that "Service Host: Local System" was making very heavy use of the hard drive bandwidth; it looked like the machine was probably disk-bound, not CPU-bound. Sysinternals Process Monitor indicated that this was probably because of some Windows Update activity.

I opened the Settings app and realized that this was correct. Windows Update was downloading: Cumulative Update for Windows 10 Version 1607 for x64-based Systems (KB4013429).

It said "Downloading updates 95%".

And it continued to say "Downloading updates 95%", for hours.

Was it stuck?

Answer

Windows Update has the capability to be exceedingly windy and verbose. Even if it only downloads one small update, it can still generate three types of logs telling you what happened.

These three types of logs are:

• The text file which the PowerShell Get-WindowsUpdateLog cmdlet saves to your desktop.

  
  
  
  
  • This is a static file; to update it, you must run the cmdlet again.
  
  



• Event Viewer > Applications and Services Logs > Microsoft > Windows > WindowsUpdateClient > Analytic.

  
  
  
  
  • This is an analytic log, so you must unhide and enable it, then must wait quite a while for it to start filling up with the first few items.
  
  



• Event Viewer > Applications and Services Logs > Microsoft > Windows > WindowsUpdateClient > Operational.

  
  
  
  
  • This log is visible by default.
  
  

I looked at the first of these three logs, then in a recently-created subfolder of C:\WINDOWS\SoftwareDistribution\Download. I soon realized that Windows Update was indeed still downloading updates, even though the progress indicator appeared stuck at 95%.

Eventually (maybe after several hours), Windows Update finished its downloading. It announced that the updates were ready to install.