After some fiddling with the server now I have broken RAID1 with the
"current" mirror on the disk with few unreadable sectors. If I try to
re-add other disk to the mirror resync goes till those bad sectors and
then starts from the beginning. And so on.
Is it possible to somehow force resync to continue even after errors?
Manual resync with dd would require a bit too long downtime. If it
is impossible to force resync I'll probably manually rsync all the
files from the old broken disk to the new one.