Question: do FC SANs have two layers of file systems? For example, the first layer being ZFS to create a comstar LUN and then you format the LUN to NtFS from the windows client?
So a LUN is a Logical unit Number, to a SAN a LUN is just a file sitting in a Volume, the SAN doesnt care what is inside the LUN its just a file (it doesnt care as it leaves everything upto the client).
The LUN once created can be mounted to another system as a Raw Data Mapping(such as adding a drive to a windows host) in this case the LUN would be formatted with NTFS.
In a VMware system a LUN could be mapped as a datastore and would be formatted with VMFS(Virtual machine File System) Then you would have a VMDK(Virtual Machine Disk) which you could install a client onto such as windows therefore formatting the VMDK as NTFS.
So yes there can be multiple layers, and multiple file systems.