How many layers are in the Isilon clustering architecture?

Which node type provides CPU, memory, and Fibre Channel connectivity?

Which Isilon OneFS job, that runs manually, is responsible for examining the entire file system for inconsistencies?

A customer has a supported cluster with the maximum protection level. How many simultaneous node component failures can Isilon OneFS sustain while still allowing full access to the entire file system and dataset?

A customer wants an N+3 protection level on their cluster. What is the minimum number of nodes they need to achieve that level of protection?