The Storage Systems (such as disk devices) used today are "dumb" devices from the user and application point of view. Each system or a device has some number of blocks - fixed-size data segments, for example 1K (1024 bytes) in size. When the disk device is connected to a computer, it can process only very simple requests, such as:
Disks can be connected to computers using IDE, SCSI, or FDDI interfaces. These interfaces are used to send commands and data to the disks, and to retrieve the data and command completion codes from the disks.
Storage Systems themselves do not create any other structures, meaning that a disk device cannot create "files" or "file directories". The only thing these systems work with are blocks, and all they can do is read and write those blocks.