Ive had multiple HDD failures with my servers and thats always troublesome.
Webservers usually can rely on raid but even then it takes a good amount of time until all data is back after a HDD replacement (most likely several days if there is lots of data).
Root server in most cases require to do manual backups (most root servers come with a ftp backup server). If backups were taken then there is a good chance to restore everything with minimal loss.
Im pretty sure people are already working on it to get everything back online.