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Disk families used in personal computers
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Notable disk families include:
· Bit Serial Interfaces - These families connected to a hard disk controller with three cables, one for data, one for control and one for power. The hard disk controller provided significant functions such as serial to parallel conversion, data separation and track formating, and required matching to the drive in order to assure reliability.
o ST506 used MFM (Modified Frequency Modulation) for the data encoding method.
o ST412 was available in either MFM or RLL (Run Length Limited) variants.
o ESDI (Enhanced Small Disk Interface) was an interface developed by Maxtor to allow faster communication between the PC and the disk than MFM or RLL.
· Word Serial Interfaces These families connect to a host bus adapter (today typically integrated into the "North Bridge") with two cables, one for data/control and one for power. The earliest versions of these interfaces typically had a 16 bit parallel data transfer to/from the drive and there are 8 and 32 bit variants. Modern versions have serial data transfer. The word nature of data transfer makes the design of a host bus adapter significantly simpler than that of the precursor hard disk controller.
o Integrated Drive Electronics (IDE) was later renamed to ATA, and then later, PATA ("parallel ATA", to distinguish it from the new serial ATA interface, SATA). The name comes from the way early families had the hard disk controller external to the disk. Moving the hard disk controller from the interface card to the disk helped to standardize interfaces, including reducing the cost and complexity. The 40 pin IDE/ATA connection of PATA transfers 16 bits of data at a time on the data cable. The data cable was originally 40 conductor, but later higher speed requirements for data transfer to and from the hard drive led to an "ultra DMA" mode, known as UDMA, which required an 80 conductor variant of the same cable; the other conductors provided the grounding necessary for enhanced high-speed signal quality. The interface for 80 pin only has 39 pins, the missing pin acting as a key to prevent incorrect insertion of the connector to an incompatible socket, a common cause of disk and controller damage.
o EIDE was an unofficial update (by Western Digital) to the original IDE standard, with the key improvement being the use of DMA to transfer data between the disk and the computer, an improvement later adopted by the official ATA standards. DMA is used to transfer data without the CPU or program being responsible to transfer every word. That leaves the CPU/program/operating system to do other tasks while the data transfer occurs.
o SCSI (Small Computer System Interface) was an early competitor with ESDI, originally named SASI for Shugart Associates. SCSI disks were standard on servers, workstations, and Apple Macintosh computers through the mid-90s, by which time most models had been transitioned to IDE (and later, SATA) family disks. Only in 2005 did the capacity of SCSI disks fall behind IDE disk technology, though the highest-performance disks are still available in SCSI and Fibre Channel only. The length limitations of the data cable allows for external SCSI devices. Originally SCSI data cables used single ended data transmission, but server class SCSI could use differential transmission, and then Fibre Channel (FC) interface, and then more specifically the Fibre Channel Arbitrated Loop (FC-AL), connected SCSI hard disks using fibre optics. FC-AL is the cornerstone of storage area networks, although other protocols like iSCSI and ATA over Ethernet have been developed as well.
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o SATA (Serial ATA). The SATA data cable has one data pair for differential transmission of data to the device, and one pair for differential receiving from the device, just like EIA-422. That requires that data be transmitted serially. The same differential signaling system is used in RS485, LocalTalk, USB, Firewire, and differential SCSI.
o SAS (Serial Attached SCSI). The SAS is a new generation serial communication protocol for devices designed to allow for much higher speed data transfers and is compatible with SATA. SAS uses serial communication instead of the parallel method found in traditional SCSI devices but still uses SCSI commands for interacting with SAS.
Manufacturers
This does not cite any references or sources.
The technological resources and know-how required for modern drive development and production mean that as of 2007, over 98% of the world's hard disks are manufactured by just a handful of large firms: Seagate, Western Digital, Samsung, and Hitachi which owns the former disk manufacturing division of IBM. Fujitsu continues to make mobile- and server-class disks but exited the desktop-class market in 2001. Toshiba is a major manufacturer of 2.5-inch and 1.8-inch notebook disks. ExcelStor is a small HDD manufacturer.
Dozens of former hard disk manufacturers have gone out of business, merged, or closed their hard disk divisions; as capacities and demand for products increased, profits became hard to find, and the market underwent significant consolidation in the late 1980s and late 1990s. The first notable casualty of the business in the PC era was Computer Memories Inc. or CMI; after an incident with faulty 20 MB AT disks in 1985.[10] CMI's reputation never recovered, and they exited the hard disk business in 1987. Another notable failure was MiniScribe, who went bankrupt in 1990 after it was found that they had "cooked the books" and inflated sales numbers for several years. Many other smaller companies (like Kalok, Microscience, LaPine, Areal, Priam and PrairieTek) also did not survive the shakeout, and had disappeared by 1993; Micropolis was able to hold on until 1997, and JTS, a relative latecomer to the scene, lasted only a few years and was gone by 1999, after attempting to manufacture hard disks in India using a second hand factory. Rodime was also an important manufacturer during the 1980s, but stopped making disks in the early 1990s amid the shakeout and now concentrates on technology licensing; they hold a number of patents related to 3.5-inch form factor hard disks.
This list is incomplete; you can help by expanding it.
· 1989: Seagate Technology bought Control Data's high-end disk business, as part of CDC's exit from hardware manufacturing.
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· 1990: Maxtor buys MiniScribe out of bankruptcy, making it the core of its low-end disk division.
· 1994: Quantum bought DEC's storage division, giving it a high-end disk range to go with its more consumer-oriented ProDrive range, as well as the DLT tape drive range.
· 1995, Conner Peripherals, which was founded by one of Seagate Technology's co-founders along with personnel from MiniScribe, announces a merger with Seagate, which was completed in early 1996.
· 1996: JTS merges with Atari, allowing JTS to bring its disk range into production. Atari was sold to Hasbro in 1998, while JTS itself went bankrupt in 1999.
· 2000: Quantum sells its disk division to Maxtor to concentrate on tape drives and backup equipment.
· 2003: Following the controversy over mass failures of its Deskstar 75GXP range, hard disk pioneer IBM sold the majority of its disk division to Hitachi, who renamed it Hitachi Global Storage Technologies (HGST).
· December 21, 2005: Seagate and Maxtor announced an agreement under which Seagate would acquire Maxtor in an all stock transaction valued at $1.9B. The acquisition was approved by the appropriate regulatory bodies, and closed on May 19, 2006.
Assignments
Task III. Give equivalents of the following computer word combs with nouns used as modifiers.
Platter surface; hard disk drive; frequency modulator; read & write heads; actuator arm (access arm); media transfer rate; hard disk capacity; storage capacity; access time; areal density transfer rate; activity level.
Task IV. Translate & remember the following phrases, make sentences of your own, using these phrases:
To be composed of; in the middle of; to be in close proximity; to prevent from; to be available for; so far as; a real time counter; time-space trade off; to be common practice; in order to; to result in; in discrepancy; the compatibility with; to be suited to use; in fact; to be commonly used; the installing system; to be available; on retail store shelves; to be as follows; to be in motion; in particular; due to…; to deal with; wear & tear; to perform something on demand; to make something essential for; lead to a loss of data; to be responsible for; to be designed to; to go bankrupt.
Task V. Topics for discussion:
Hard disk is a storage device. Dwell on its development, functions & applications. What do discrepancies of reposted & specified capacities consist in?
Task VI. Role-play
At the trade exhibition. Act out the discussion between the seller & buyer on the advantages of exposed hard disk.
Task VII. What do the following acronyms stand for? Match the equivalents.
SCSI, SATA, PATA, SAS, HDD, NAS, SAN, GMR, S.M.A.R.T.
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interface Parallel Advanced Technology Attachment interface,
interface - Serial Advanced Technology Attachment interface,
Small Computer System Interface, Serial Attached SCSI,
Hard Disk Drive, Hard Drive, Network Attached Storage,
Storage Area Networks, Giant MagetoResistive,
self monitoring, analysis and reporting technology
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