@JCalMN Yes, that’s right. The underlying compression bug was causing the other patches to fail on some SSDs. This fixes that problem.
— Gabriel Aul (@GabeAul) December 16, 2014
We recently released an update for the Windows 10 Technical Preview (Build 9879) to fix an issue with frequent Explorer.exe crashes – KB3020114. We’re releasing a few fixes to the most painful issues hitting Windows Insiders on this build since we won’t have a full new build until early 2015, and we want to keep it usable for you through the end of the year.
Unfortunately, as many of you discovered there was a problem that affected about 12% of PCs when installing this update, causing the install to fail.
The issue occurs due to 2 underlying bugs:
In build 9879 we introduced some new System Compression code that systems with SSDs can take advantage of to reduce disk usage by the OS. In some cases the logic for low-space detection gets inverted, and we compress automatically as a background operation.
On PCs have had system compression enabled, an additional bug with how the filesystem tracks deletes caused the installer to think that the temp files failed to extract correctly, so the installer fails because it thinks it cannot complete.