Many unrepairable corrupted Defender files found by sfc /scannow

Thanks. I've told Brink about this.

I can understand the logic of it but it had never occurred to me before.
- Without any source being available, there is nowhere for any replacement files to come from given that SFC has already checked the component store.
- WU & hence the internet acts as a default source when DISM /RestoreHealth /Source:nnnnnnnnnnn is not specified.

Bree - Since you have now demonstrated the internet requirement I can test use of the ISO as the source if there is a reoccurence. It will merely be a training exercise - it will not fix the fault in this particular instance because we already know that the problem is caused by a later update

Denis

Farvatten,

I have not experimented with Windows Update Delivery Optimization for years. I could never get it to work for my fairly standard workgroup-based home network and understood that Windows Update Delivery Optimization was only applicable to managed domains.

Is your network a managed domain or does Windows Update Delivery Optimization work for standard peer-to-peer workgroup-based networks after all?

Denis

Thanks to you both.

I'll try it out. The only updates that I do not already share, after downloading once from the MS update catalog for use on all 3 computers, are Windows defender definition [& platform] updates.

Denis

Try3 said:

The only updates that I do not already share ... are Windows defender definition [& platform] updates.

Now here's the thing about the Optimizer, not all types of downloads appear to be shared. For instance during CU Tuesday's I'll watch both of my internet traffic histograms running on each optimized machine, where it's visually clear what's leaving one is being downloaded to the other. What I have not seen shared are downloads of Windows Malicious Software Removal Tool nor Adobe Flash Security updates. Because WD Platform changes typically come in at these off hours and get installed at odd times I also can't verify that they get shared, nor WD Definition updates for that matter but I'll try and keep my eyes open for evidence now that the question has been raised.

Updated: to Reflect @Try3 's Optimization research link:

Configure Delivery Optimization for Windows 10 updates - Microsoft Docs

Farvatten,

This says that WD definitions can be shared - Configure Delivery Optimization for Windows 10 updates - Microsoft Docs
however
I do not use WU but MpCmdRun.exe -SignatureUpdate for my WD updates so it might not apply to this.

I'll have to leave it until the next platform update so I stand a chance of differentiating between direct MS downloading & use of delivery optimisation.
- Given that delivery optimisation still involves checking data with MS it may not be simple telling the difference.
- I have found a PowerShell monitoring facility described at Measuring Delivery Optimization and its impact to your network - Microsoft Tech Community - 301809 but, as it says there, the download must be started and then PowerShell monitoring can begin so I'll need a large-ish download and quick reactions to capture anything.

I have a larger mobile data allowance these days [my phone is my internet connection & I have a monthly allowance of 12GB] so it is not the end of the world either way. My earlier attempts to share WD updates by copying them from C:\Windows\SoftwareDistribution\Download caused WD definitions updating to lock up completely even though I stepped through carefully copying each update in the correct sequence from one computer to another.

Denis

Denis