Brusk answer - a very long time.

I had reason to take my Organization One below back to an earlier organisation epitome and upgrade it to 1903 again. In fact, the prototype I restored for this motorcar was its 1511 image from mid-2016. I then upgraded this to 1809 using an ISO in about two hours.

Just for fun (?) I decided to let Windows Update perform the Feature Update to version 1903. Now this auto had previously been updated from 1809 to 1903 using an ISO, so I knew that method took no more than a couple of hours. How much longer could Windows Update have?

Well, it would be expected to to take a picayune longer, considering information technology uses the Unified Update Platform (UUP). This is designed to reduce the download size of an update by merely downloading the changes, non the total set of files as are used in the ISO.

Microsoft said:

...one of the biggest benefits UUP brings to our customers is a reduction in download size of build updates on PCs.... Differential download packages rely on re-using files on your electric current OS to reconstruct the newer Os. This could include copying files as-is that have not changed betwixt builds, or information technology could involve applying �binary deltas�� or �diffs�� to old files to generate newer files. Differential download packages are smaller and tin can have a shorter amount of fourth dimension to download.

For a full build, we refer to this as a canonical download package... Canonical download packages tend to exist larger in size and may take longer to download.

..equally nosotros coil out UUP in our retail release, users can look their download size to decrease by approximately 35% when going from one major update of Windows to another. For retail users, the first time they get the UUP client lawmaking is part of the Creators Update, therefore, they will see the do good of differential download packages when they get from the Creators Update to the adjacent feature update of Windows.

An update on Unified Update Platform (UUP) for Windows 10

So, the download is smaller, but there's more work to do with it after downloading. I told Window Update to 'Download and install at present', ready the stopwatch going and opened Task Manager to sentinel what was going on.

The beginning step was Windows Update maxim "Getting gear up". This stage took xv minutes to complete, then the download began.

Windows Update said "Downloading - 0%" which climbed steadily to 99% while Task Manager showed steady download progress. Network activity nigh ceased later iii.5GB had been downloaded in 15 minutes (this time is entirely dependent on your broadband speed).

The step from "Downloading - 99%" to "Downloading - 100%" took an astonishing 42 minutes, during which there was fiddling or no network activity just a lot of CPU activity, by and large from the Windows Installer. This would presumably be the "applying �binary deltas�� or �diffs�� to quondam files to generate newer files" stage.

Then Windows Update first said "Awaiting install" and so quickly switched to "Installing - 0%"....

....Paint would take dried quicker - it took a further three hours and x minutes to get to "Installing - 100%" and asking me to select a restart time to complete the install.

Then, on the restart, it rejoined the same steps of 'installing updates' and restarts that an ISO upgrade would accept followed, taking a farther 40 minutes.

So, in conclusion what would accept less than two hours with an ISO (I know, considering I accept previously used the 1903 ISO on this machine) took over four and a half hours via Window Update. I tin't say I'yard that impressed. At least it worked reliably, I'll give it that. And I suppose I could have continued using the machine while the update ground away in the background (I didn't though, I went out for an hour or so instead). At to the lowest degree I now sport a prissy entry in the Update History.....

How long does the 1903 upgrade take using Windows Update?-image.png