You have a FreeNAS 7/NAS4Free server setup and you have several USB drives attached to it. Your ongoing issue is that every time you reboot your FreeNAS server the disk mounts get mixed up and the drive numbers are out of order. One day your 120GB Western Digital HDD is da0, then all of a sudden it becomes da2 while your Seagate 500GB HDD is now da0.
If you have more USB drives attached and you use software RAID. All of a sudden, your Western Digital HDD that stores all those vacation pictures becomes a member of a RAID set. Ouch!!