you did many posts so I thought you could be member of the team :)
So I should compile the DRDB 8.4 module myself like I did earlier on Version 1.9. Then I also have to compile the right drbd-tools.
I could not believe to completly erase my DRBD-Store (6 TB) to do the update to...
I have the same kind of problem. But my guest FS is BTRFS. It was an read error on vda1 but BTRFS self healing features read it from another block and the where no more errors on this.
...waiting for DRBD9 :)