I have seen this before but it always reported correctly after a restart.
That is true until the next update and the same will repeat. No big deal but it shows the elementary simple math was not done correctly.
The explanation is that many of the files apparently stored for the Windows Update Backups (in the WinSxS folder) are not actually there. Each backup may need to keep many of the same files as earlier or later backups. It would be silly to store the same file multiple times, so there is only one physical copy, but each backed up version that need to have a it listed in its folder has a hard link to the one physical copy.
For all practical purposes a hardlink looks like a file, complete with all its properties. Most windows apps like File Explorer and Disk Cleanup don't distinguish between a physical file and a hard link. If there are many such hard links in a folder then the size will be misreported, each one will be counted when adding up the total apparent size occupied by the files. After some cumulative updates there seem to be a lot of hard links, that's all. Disk Cleanup still has to delete them all even if many are hard links. That's why it can take a long time to run.
https://technet.microsoft.com/en-GB/.../dn251566.aspxA 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.
I manually do a disk cleanup after each Windows 10 update and every time the Windows Update Cleanup index is pointing to a 3.99TB. This has been the case from early this year when I started paying attention to the lengthening disk cleanup time. The disk space needs cleanup between two consecutive updates cannot possibly be 3.99TB by any imagination.
I am not using Disk Cleanup anymore to get rid of older Windows Update leftovers. It takes ages to do so.
Hope this helps,
- Hardlink or hardlinks cannot be created for directories (folders). Hard link can only be created for a file.
- Symbolic links or symlinks can link to a directory (folder).
- Removing the original file that your hard link points to does not remove the hardlink itself; the hardlink still provides the content of the underlying file.
- If you remove the hard link or the symlink itself, the original file will stay intact.
- Removing the original file does not remove the attached symbolic link or symlink, but without the original file, the symlink is useless (the same concept like Windows shortcut).
Thanks for the inputs. However, they don't appear on giving any light about this 3.99TB disk space (on a 100GB HDD) reported used by Windows Update. Let me repeat about how this 3.99TB appeared on my screen:
(1) Up-to-date Windows 10 Pro updates were installed.
(2) Disk Cleanup was manually performed: 3.99TB Windows Update Cleanup was observed (and selected for cleanup.
(3) After a few days, up-to-date Windows 10 Pro updates came in and they were installed.
(4) Disk Cleanup was manually performed: 3.99TB Windows Update Cleanup was observed (and selected for cleanup).
The above is true to this day.
I don't manually create and delete any system files and only use the laptop for browsing on the Internet. I don't see how a windows update cycle between 2 complete Disk Cleanup can stack up a use of 3.99TB disk space on a 100GB HDD in the first place - the complete Windows 10 Pro install on my laptop only takes a total of about 30GB.
Until the entire update stack switches over to the Unified Update Platform (UUP) present in the Insider Preview, Cumulative Updates carry forward previous updates from earlier cumulative update items. I first blogged about this in early October, right after the problem initially appeared in KB3194798. I based my blog post on the same information that Bree provided to you earlier, and it remains as true now as it was then. Something Microsoft did to the update files in that particular KB caused this behavior and it persisted in Windows 10 Pro until about two cumulative updates ago. I understand it's still present in Windows 10 Home. You aren't doing anything to cause this: it's a characteristic of the particular update files involved. To make things worse, it takes 15+ minutes to run Disk Cleanup to get rid of this stuff, with another 15 minutes worth of pre-shutdown cleanup to follow the next time you restart or shut down. All you can do is hope that MS fixes this soon, and deal with the situation until then.
On my T500 laptop with a 3.09 GHz Core Duo processor, Disk Cleanup after a Windows 10 Cumulative Updates takes about 4 hours to finish now, which was the reason for me to check out the details of the cleanup list in the first place and noticed this come-no-where 3.99TB Windows Update Cleanup space in the list. As I recall a similar Disk Cleanup took no more than 10 to 15 minutes last year. For now, Disk Cleanup immediately after a windows update is the last thing I do before going to bed.
Thank you for sharing your insights.