These are commands to backup and restore files from an external disk. At first, access was through proprietary software distributed on a 5.25-inch floppy disk. However, cartridges were expensive to manufacture compared to making a floppy disk or CD-ROM. See also history of IBM magnetic disk drives. This is accessible only by formatting a floppy as an "MS-DOS startup disk". Most storage networks use the SCSI protocol for communication between servers and disk drive devices. Limited to 128 partitions per disk. The amount of disk space System Restore consumes can be configured. This layer is concerned with the physical operation of the storage device (e.g. disk). Images are usually stored on a hard disk. These are the fast head positioners for rigid-disk ("hard disk") drives. It allows users to try Fedora without making changes to the hard disk. This lets them operate like the hard disk of a personal computer. It is one of the first albums recorded onto a hard disk. Such a device may be described as a ladder mounted on a turnable disk.