It disabled my mirrored drive without any warning or notification. It just shows up as a striped volume now.
I started noticing it after Windows 10 Insider Preview 17046.1000 installed, my pc started complaining about a missing page file. ( which was on the raid1 volume).
Apparently uSoft knows about this issue, and a fix is promised although info is hard to come by.
The 17046 announcement mentions this under known issues, quote:
All types of dynamic volumes listedherewill not mount properly or be accessible from Windows. The data remains intact on the volume, it is just not accessible from this OS build. If you need access to the data you can roll back to an earlier build. A fix for this issue will be released in the next build.
This issue deserves more visibility, as folks may be panicking and in the process of trying to "fix" this problem will probably lose their data for good. So the prudent course of action: If you can live without the data for a while, just wait for an update that fixes this.