Doing it Wrong Worked: Replacing a Flaky Disk in Windows RAID 1

I had a disk failing, and had to remove it. The "right" way is to break the mirror or remove the disk from the plex, but it was preventing a boot for the third time, so I shut down and removed it.

The computer booted from the second disk (after selecting it with the F10 boot menu, then the Windows boot menu).

So I added the replacement disk, restarted, and then went to work on rebuilding the mirror.

The new disk was initialized as MBR.

The remaining disk in the RAID plex was working, but the plex was gone. When I tried to reactivate the volume, it said the plex was gone.

So I had to select "Remove Mirror..." on the functional volume. It showed two disks, one of which was missing. I deleted the missing disk, and the volume went back to being a regular volume.

If there's a volume on the new disk, delete it.

Then, right-click on the functional volume and choose "Add Mirror...". It'll create a volume on the new disk.

If the new disk is a little smaller, it won't show the menu item because there's not enough space. The solution is to resize the functional volume, shrinking it so it's smaller than the free space on the new disk.