Disk storage is a general category of storage mechanisms where data is recorded by various electronic, magnetic, optical, or mechanical changes to a surface layer of one or more rotating disks. A disk drive is a device implementing such a storage mechanism. Notable types are the hard disk drive (HDD) containing a non-removable disk, the floppy disk drive (FDD) and its removable floppy disk, and various optical disc drives (ODD) and associated optical disc media.
A floppy disk, also known as a floppy, diskette, or simply disk, is a type of disk storage composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic enclosure lined with fabric that removes dust particles. Floppy disks are read and written by a floppy disk drive (FDD).
FASTRAND was a magnetic drum mass storage system built by Sperry Rand Corporation for their UNIVAC 1100 series and 418/490/494 series computers. A FASTRAND subsystem consisted of one or two Control Units and up to eight FASTRAND units. A dual-access FASTRAND subsystem included two complete control units, and provided parallel data paths that allowed simultaneous operations on any two FASTRAND units in the subsystem. Each control unit interfaced to one 1100 Series (36-bit), or 490 Series (30-bit), parallel I/O channels.
Click of death is a term that became common in the late 1990s referring to the clicking sound in disk storage systems that signals a disk drive has failed, often catastrophically.
Quantum Corporation is a manufacturer of data storage devices and systems, including tape drive and disk-based systems. The company's headquarters is in San Jose, California. From its founding in 1980 until 2001, it was also a major disk storage manufacturer, and was based in Milpitas, California. Quantum sold its hard disk drive business to Maxtor in 2001 and now focuses on integrated storage systems.
Floptical refers to a type of floppy disk drive that combines magnetic and optical technologies to store data on media similar to standard 3 1⁄2-inch floppy disks. The name is a portmanteau of the words "floppy" and "optical". It refers specifically to one brand of drive and disk system, but is also used more generically to refer to any system using similar techniques.
IBM manufactured magnetic disk storage devices from 1956 to 2003, when it sold its hard disk drive business to Hitachi. Both the hard disk drive (HDD) and floppy disk drive (FDD) were invented by IBM and as such IBM's employees were responsible for many of the innovations in these products and their technologies. The basic mechanical arrangement of hard disk drives has not changed since the IBM 1301. Disk drive performance and characteristics are measured by the same standards now as they were in the 1950s. Few products in history have enjoyed such spectacular declines in cost and size along with equally dramatic improvements in capacity and performance.
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact. The term is a portmanteau of the words static and friction, perhaps also influenced by the verb stick.
In optical storage, constant angular velocity (CAV) is a qualifier for the rated speed of any disc containing information, and may also be applied to the writing speed of recordable discs. A drive or disc operating in CAV mode maintains a constant angular velocity, contrasted with a constant linear velocity (CLV).
Cylinder-head-sector (CHS) is an early method for giving addresses to each physical block of data on a hard disk drive.
Millipede memory is a non-volatile computer memory stored on nanoscopic pits burned into the surface of a thin polymer layer, read and written by a MEMS-based probe. It promised a data density of more than 1 terabit per square inch, which is about the limit of the perpendicular recording hard drives. Millipede storage technology was pursued as a potential replacement for magnetic recording in hard drives, at the same time reducing the form-factor to that of flash media. IBM demonstrated a prototype millipede storage device at CeBIT 2005, and was trying to make the technology commercially available by the end of 2007. However, because of concurrent advances in competing storage technologies, no commercial product has been made available since then.
Conner Peripherals was a company that manufactured hard drives for personal computers. Conner Peripherals was founded in 1985 by Seagate Technology co-founder and San Jose State University alumnus Finis Conner. In 1986, they merged with CoData, a Colorado start-up founded by MiniScribe founders Terry Johnson and John Squires. CoData was developing a new type of small hard disk that put the capacity of a 5.25-inch drive into the smaller 3.5-inch format. The CoData drive was the first Conner Peripherals product. The company was partially financed by Compaq, who was also a major customer for many years.
Embedded servo or wedge servo is a type of servo configuration used on hard disks. Embedded servo systems embed the feedback signals for the read/write head positioner inside gaps (wedges) in the data tracks of the disk. This setup allows the entire set of platters to be used, instead of having to reserve one or two surfaces for the servo's use, which makes more space for data available on the drive. Embedded servo was originally developed in the 1970s, and started to appear on mass-market hard drives for personal computers in the late 1980s.
Storage Module Drive (SMD) is a family of storage devices that were first shipped by Control Data Corporation in December 1973 as the CDC 9760 40 MB (unformatted) storage module disk drive. The CDC 9762 80 MB variant was announced in June 1974 and the CDC 9764 150 MB and the CDC 9766 300 MB variants were announced in 1975. A non-removable media variant family of 12, 24 and 48 MB capacity, the MMD, was then announced in 1976. This family's interface, SMD, derived from the earlier Digital RP0x interface, was documented as ANSI Standard X3.91M - 1982, Storage Module Interfaces with Extensions for Enhanced Storage Module Interfaces.
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs) and 2048 bytes for CD-ROMs and DVD-ROMs. Newer HDDs use 4096-byte (4 KiB) sectors, which are known as the Advanced Format (AF).
An electrohydraulic servo valve (EHSV) is an electrically operated valve that controls how hydraulic fluid is sent to an actuator. Servo valves are often used to control powerful hydraulic cylinders with a very small electrical signal. Servo valves can provide precise control of position, velocity, pressure, and force with good post movement damping characteristics.
The floppy disk is a data storage and transfer device which was ubiquitous from the mid-1970s well into the 2000s. Besides the 3½-inch and 5¼-inch formats used in IBM PC compatible systems, or the 8-inch format that preceded them, many proprietary floppy disk formats were developed, either using a different disk design or special layout and encoding methods for the data held on the disk.
Higher performance in hard disk drives comes from devices which have better performance characteristics. These devices include those with rotating media, hereby called rotating drives, i.e., hard disk drives (HDD), floppy disk drives (FDD), optical discs, and it also covers devices without moving parts like solid-state drives (SSD). For SSDs, most of the attributes related to the movement of mechanical components are not applicable, but the device is actually affected by some other electrically based element that still causes a measurable delay when isolating and measuring that attribute. These performance characteristics can be grouped into two categories: access time and data transfer time.
