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Cleanup 3.99 TB from 500GB Drive!

Yesterday was Patch Tuesday, and included another Cumulative Update: KB3194798. This one included a bit of a surprise. Cleanmgr.exe offered to cleanup 3.99 TB from my 500 GB C: drive. It’s best appreciated from this screen cap:

That’s not something you see often on a 500GB drive!

How Can You Cleanup 3.99 TB from a 500GB Drive?

As it happens, Windows Update files reside in the Windows Component Store (aka the WinSxS folder) along with OS components. Though these files are reported elsewhere in the disk structure, too, they really reside in WinSxS, and are linked to other folders. Thus, for example Notepad.exe really resides in WinSxS, but shows up in C:\Windows in the “Location” field on the General properties tab in File Explorer.

Here’s what the Windows IT Center article “Determine the Actual Size of the WinSxS Folder” says about file size reports:

For operating system files, it can appear that more than one copy of the same version of a file is stored in more than one place on the operating system, but there’s usually only one real copy of the file. The rest of the copies are just “projected” by hard linking from the component store. A hard link is a file system object that lets two files refer to the same location on disk. Some tools, such as the File Explorer, determine the size of directories without taking into account that the contained files might be hard linked. This might lead you to think that the WinSxS folder takes up more disk space than it really does.

This set of update files must be hard-linked all over the place. That explains why their reported size vastly exceeds the 1.3 GB of actual disk space that they occupy. The number was good for a chuckle, however. It also provided an opportunity for me to learn something useful and interesting about the WinSxS folder. There’s more going on than you might think when it’s time to cleanup 3.99 TB of update files.

One More Thing…

This particular cleanup takes a looooong time to complete, so be patient. It averaged between 15 and 20 minutes on my Windows 10 PCs. After it’s done, you’ll want to restart your PC. Then brace yourself, because cleanups will continue for another 15 minutes or more before the machine shuts down and restarts. Apparently, there’s a LOT of cleanup involved here!

[Note: thanks to TenForums user Bree whose forum comment brought the cited TechNet article, and its WinSxS explanation, to my attention.]