If we go back to the SNIA Shared Storage Model we have an application layer. Our application will either issue a record request or a file I/O request. Our file system or database will take that file I/O or record I/O request and convert it to a block I/O request.
The block I/O request will then come down through our block aggregation layer. It’s the block I/O request from the file system that will feed through our virtualization layer. Our virtualization layer is in our block aggregation layer.
File system virtualization could be software based or the new hardware components that can read multiple file systems from NAS appliances and then make it look like one big file system.