Too many times i’ve seen filmakers with their hard heartfelt work brought to me to output on a firewire drive to find that their drive wont mount or making clicking sounds. Both are bad and mean that the drive is failed in some way. Most people will try to repeatedly plug the drive into the computer and hope it will come up, this is really not the safest approach. Most portable drives are RAID0 meaning that there are 2 or more drives stripped together to make up the drive that the computer sees. This is not at all protected but many people are fooled by the term RAID on the box. If one of these drives have failed and will not mount a very expensive recovery procedure is available by companies like Drive Savers. Drive recovery can be tricky but can be successful. Some of the best practices before a a failure is to use RAID1, RAID 5, RAID 6, drive systems which have built in recovery mechanisms. As always though multiple backup drive or medium (like LTO backup) is the safest way to protect your edit data or OCN (original camera negative) masters.