hard disk interfaces

Today's hard drives use SATA or SAS interfaces, which are the serial versions of their PATA and SCSI predecessors. SATA drives are found in every personal computer, and SAS drives, which are enterprise class, are found in servers and high-end workstations.

Following are the major types, including older ones for comparison. Although drives use the run length limited (RLL) encoding, the encoding method is not prescribed by the interface. See SATA, serial attached SCSI, RAID, RLL and hard disk.

HARD DISK INTERFACES Transfer Rate (MB per Max.Type Encoding** sec) Storage SATA RLL 150-600 14TB SAS RLL 375-750 12TB Older Interfaces PATA RLL 3-133 1TB SCSI RLL 5-320 1TB IPI RLL 10-25MB 3GB ESDI RLL 1-3MB 2GB SMD RLL 1-4MB 2GB ST506 RLL RLL 937KB 200MB ST506 MFM MFM 625KB 5MB

The First RAID System

Using SCSI disks, this prototype was built by University of Berkeley graduate students in 1992. Housing 36 320MB disk drives, the total storage of this entire rack was a whopping 11GB. See RAID. (Image courtesy of The Computer History Museum, www.computerhistory.org)

Twenty Five Years Later

In 2017, this single 10TB hard drive had 900 times as much storage as the 36 drives in the Berkeley system above.