Bad Block Management in RAID1 and "Faulty"

Hi Group , I would like to understand more about bad block management ( esp RAID1 )that given the below link http://neil.brown.name/blog/20100519043730 . Highly appreciate any kind of help.

1) What happens when a write comes on a known bad block ?.

2) When exactly the raid1 decides to make the device "Faulty"? Does that depends on the number of bad blocks in the list ie: 512?

Thanks,
Ankur