There are a lot of moving parts in storage virtualization. Storage systems either provide block or file storage. Block storage typically uses iSCSI or FCoE while file storage typically uses NFS or CIFS/SMB. As virtualization abstracts the underlying hardware, so too does storage virtualization abstract the physical storage resources. Virtualization attempts to present the virtual machine with storage resources and then does the emulation or mapping to the actual physical storage location. The mapping of virtual to physical storage is maintained in a mapping table called meta-data.
The hypervisor uses the meta-data to map I/O requests from the logical location on the virtual disk into I/O requests on the physical disk. Storage virtualization allows logical storage representations to be aggregated into storage pools. This allows storage resources to scale up significantly and be transparent to the virtual machine using the storage. Logical disks or virtual disks are made...