Comment # 7 on bug 939748 from Neil Brown

> Just for the record the problem happened after a recent update!!

That is surprising as there hasn't been a recent update for mdadm in 13.2
(I assume are using straight 13.2, not Tumbleweed of factory?).

Maybe it was an update to dracut changing the way mdadm is run at early boot or
something.  I cannot see anything in the logs though.

>  the second is to restore my win data.

I doubt that is possible unless you have backups - I wish that were not so.

The fact that the partition tables reported above show both sda and sdb have a
btrfs partition and an xfs partition suggest that one was copied over the
other.
You could try:
  cmp -l /dev/sda /dev/sdb

to get an idea of how much is the same and how much is still different.  If
most of the device is still different it might be worth trying harder, but I
cannot help much with resurrecting windows filesystems.

I know what the cause was and how to stop it happening in future (once the
update gets installed) but that doesn't help you now.  Sorry.