File-system protocols like CIFS and NFS treat files as a single entity. For example, when a user opens a file, it's opened in its entirety and then locked to prevent others from modifying it. This is ill-suited for apps where data is accessed at a sub-file level, such as databases where small pieces of information are continuously read and updated within a larger file. Without question, block-based storage protocols like SCSI, iSCSI and FC are superior to the file-based access methods of NAS when it comes to non-file-based data access.