Its replacing a concept called vfiler on 7-mode where you could have multiple instances of the filer. i'ts not running another OS. just a thread with required client processing services and it's own routing domain
What is the concept of virtual WWN#
Replacing a File in 7-mode where the WWN were software assigned instead of using the physical HBA one. this help when you replacing the node or moving the LIF's around so you don't need to re-configure zooning (if they are WWN based).
What is the difference between Aggregate and storage pools.