How to know which disk has failed on a Mirrored Raid? marked as DR0
From an elevated command prompt run diskpart. Once you're in diskpart, run detail disk and detail volume after selecting the appropriate disk/volume using the select command. This should list the health state of each disk.
Of course, in this case, the yellow caution symbol on disk 0 is probably a good indicator :)
If you look in the disk management screen, Disk 0 is displayed with a yellow warning icon, while Disk 1 is not. I would hazard a guess that it was Disk 0 which reported the bad blocks, but you might want to investigate that yourself before pulling drives.