Misplaced Pages

#780219

54-555: SASI may refer to: Shugart Associates System Interface , the first embodiment of what is now known as SCSI SASI (software) , a student information system developed by Pearson School Systems Shiprock Associated Schools, Inc. Socialist Workers' Sport International , in German Sozialistische Arbeiter Sport Internationale Sonoran Arthropod Studies Institute ,

108-462: A parallel bus design. Since 2005, SPI was gradually replaced by Serial Attached SCSI (SAS), which uses a serial design but retains other aspects of the technology. Many other interfaces which do not rely on complete SCSI standards still implement the SCSI command protocol ; others drop physical implementation entirely while retaining the SCSI architectural model . iSCSI , for example, uses TCP/IP as

162-427: A target . The initiator sends a command to the target, which then responds. SCSI commands are sent in a Command Descriptor Block ( CDB ). The CDB consists of a one byte operation code followed by five or more bytes containing command-specific parameters. At the end of the command sequence, the target returns a status code byte, such as 00h for success, 02h for an error (called a Check Condition), or 08h for busy. When

216-586: A "LUN number" or "LUN id". In modern SCSI transport protocols, there is an automated process for the "discovery" of the IDs. The SSA initiator (normally the host computer through the 'host adaptor') "walk the loop" to determine what devices are connected and then assigns each one a 7-bit "hop-count" value. Fibre Channel – Arbitrated Loop (FC-AL) initiators use the LIP (Loop Initialization Protocol) to interrogate each device port for its WWN ( World Wide Name ). For iSCSI, because of

270-511: A "production-quantity optical drive ", the Optimem 1000, offering 1 GB of storage on 12-inch disks using a laser-based recording technology, taking advantage of a substantially increased track density compared to contemporary magnetic recording technologies. The process of recording involved focusing the laser beam on the metal layer of the disk, this causing a "decomposable polymer" layer underneath to generate "gaseous components" and to push up on

324-403: A 21-bit LBA address. The Read(10), Read(12), Read Long, Write(10), Write(12), and Write Long commands all contain a 32-bit LBA address plus various other parameter options. The capacity of a "sequential access" (i.e. tape-type) device is not specified because it depends, amongst other things, on the length of the tape, which is not identified in a machine-readable way. Read and write operations on

378-612: A Tucson, Arizona educational nonprofit. South Australian Sports Institute , an elite athlete training program in South Australia Sutherland Astronomical Society (officially Sutherland Astronomical Society Incorporated), an amateur astronomical society based in Sydney, Australia. Swanson Analysis Systems, Inc., the name Ansys was founded under Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

432-548: A distinguished career at IBM and a few years at Memorex , Alan Shugart decided to strike out on his own in 1973. After gathering venture capital , he started Shugart Associates. The original business plan was to build a small-business system (similar to the IBM 3740 ) dealing with the development of various major components, including floppy disk drives and printers. After two years, Shugart had exhausted his startup money and had no product to show for it. The board then wanted to focus on

486-459: A much broader range of options for RAID subsystems together with the existence of nearline SAS (NL-SAS) drives. Instead of SCSI, modern desktop computers and notebooks typically use SATA interfaces for internal hard disk drives, with NVMe over PCIe gaining popularity as SATA can bottleneck modern solid-state drives . SCSI is available in a variety of interfaces. The first was parallel SCSI (also called SCSI Parallel Interface or SPI), which uses

540-410: A sequential access device begin at the current tape position, not at a specific LBA. The block size on sequential access devices can either be fixed or variable, depending on the specific device. Tape devices such as half-inch 9-track tape , DDS (4 mm tapes physically similar to DAT ), Exabyte , etc., support variable block sizes. On a parallel SCSI bus, a device (e.g. host adapter, disk drive)

594-453: A transport mechanism, which is most often transported over Gigabit Ethernet or faster network links. SCSI interfaces have often been included on computers from various manufacturers for use under Microsoft Windows , classic Mac OS , Unix , Amiga and Linux operating systems, either implemented on the motherboard or by the means of plug-in adaptors. With the advent of SAS and SATA drives, provision for parallel SCSI on motherboards

SECTION 10

#1732859228781

648-522: A unified standard. In October 1981, the two companies agreed to co-develop SASI and present their standard jointly with ANSI. Until at least February 1982, ANSI developed the specification as "SASI" and "Shugart Associates System Interface". However, the committee documenting the standard would not allow it to be named after a company. Almost a full day was devoted to agreeing to name the standard "Small Computer System Interface", which Boucher intended to be pronounced "sexy", but ENDL's Dal Allan pronounced

702-421: Is a "virtual" disk—a stripe set or mirror set constructed from portions of real disk drives. The SCSI ID, WWN, etc. in this case identifies the whole subsystem, and a second number, the logical unit number (LUN) identifies a disk device (real or virtual) within the subsystem. It is quite common, though incorrect, to refer to the logical unit itself as a "LUN". Sometimes, redundantly, the actual LUN may be called

756-427: Is a 5-bit field reported by a SCSI Inquiry Command ; defined SCSI Peripheral Device Types include, in addition to many varieties of storage device, printer, scanner, communications device, and a catch-all "processor" type for devices not otherwise listed. In larger SCSI servers, the disk-drive devices are housed in an intelligent enclosure that supports SCSI Enclosure Services (SES) . The initiator can communicate with

810-487: Is a protocol that specifies how to transport SCSI commands over a reliable RDMA connection. This protocol can run over any RDMA-capable physical transport, e.g. InfiniBand or Ethernet when using RoCE or iWARP . USB Attached SCSI allows SCSI devices to use the Universal Serial Bus . The Automation/Drive Interface − Transport Protocol (ADT) is used to connect removable media devices, such as tape drives, with

864-530: Is a set of standards for physically connecting and transferring data between computers and peripheral devices , best known for its use with storage devices such as hard disk drives . SCSI was introduced in the 1980s and has seen widespread use on servers and high-end workstations, with new SCSI standards being published as recently as SAS-4 in 2017. The SCSI standards define commands , protocols, electrical, optical and logical interfaces . The SCSI standard defines command sets for specific peripheral device types;

918-416: Is considered to be the "father" of SASI and ultimately SCSI due to his pioneering work first at Shugart Associates and then at Adaptec , which he founded in 1981. A SASI controller provided a bridge between a hard disk drive's low-level interface and a host computer, which needed to read blocks of data. SASI controller boards were typically the size of a hard disk drive and were usually physically mounted to

972-555: Is identified by a "SCSI ID", which is a number in the range 0–7 on a narrow bus and in the range 0–15 on a wide bus. On earlier models a physical jumper or switch controls the SCSI ID of the initiator ( host adapter ). On modern host adapters (since about 1997), doing I/O to the adapter sets the SCSI ID; for example, the adapter often contains a Option ROM (SCSI BIOS) program that runs when the computer boots up and that program has menus that let

1026-404: Is typically for a CD-ROM drive. Note that a SCSI target device (which can be called a "physical unit") is sometimes divided into smaller "logical units". For example, a high-end disk subsystem may be a single SCSI device but contain dozens of individual disk drives, each of which is a logical unit. Further, a RAID array may be a single SCSI device, but may contain many logical units, each of which

1080-435: Is used which is also of serial nature. SCSI is popular on high-performance workstations, servers, and storage appliances. Almost all RAID subsystems on servers have used some kind of SCSI hard disk drives for decades (initially Parallel SCSI, interim Fibre Channel, recently SAS), though a number of manufacturers offer SATA -based RAID subsystems as a cheaper option. Moreover, SAS offers compatibility with SATA devices, creating

1134-718: The Macintosh Quadra 630 in 1994, and added it to its high-end desktops starting with the Power Macintosh G3 in 1997. Apple dropped on-board SCSI completely in favor of IDE and FireWire with the (Blue & White) Power Mac G3 in 1999, while still offering a PCI SCSI host adapter as an option on up to the Power Macintosh G4 (AGP Graphics) models. Sun switched its lower-end range to Parallel ATA (PATA) with introduction of their Ultra 5 and 10 low end workstations using CMD640 IDE controller and continued this trend with

SECTION 20

#1732859228781

1188-821: The Amiga 3000/3000T systems and it was an add-on to previous Amiga 500/2000 models. Starting with the Amiga 600/1200/4000 systems Commodore switched to the IDE interface. Atari included SCSI as standard in its Atari MEGA STE , Atari TT and Atari Falcon computer models. SCSI has never been popular in the low-priced IBM PC world, owing to the lower cost and adequate performance of ATA hard disk standard. However, SCSI drives and even SCSI RAIDs became common in PC workstations for video or audio production. Recent physical versions of SCSI‍—‌ Serial Attached SCSI (SAS), SCSI-over- Fibre Channel Protocol (FCP), and USB Attached SCSI (UAS)‍—‌break from

1242-554: The SCSI standards also include an extensive set of command definitions. The SCSI command architecture was originally defined for parallel SCSI buses but has been carried forward with minimal change for use with iSCSI and serial SCSI. Other technologies which use the SCSI command set include the ATA Packet Interface , USB Mass Storage class and FireWire SBP-2 . In SCSI terminology, communication takes place between an initiator and

1296-526: The controllers of the libraries (automation devices) in which they are installed. The ADI standard specifies the use of RS-422 for the physical connections. The second-generation ADT-2 standard defines iADT, use of the ADT protocol over IP (Internet Protocol) connections, such as over Ethernet . The Automation/Drive Interface − Commands standards (ADC, ADC-2, and ADC-3) define SCSI commands for these installations. In addition to many different hardware implementations,

1350-452: The drive's chassis. SASI, which was used in mini- and early microcomputers, defined the interface as using a 50-pin flat ribbon connector which was adopted as the SCSI-1 connector. SASI is a fully compliant subset of SCSI-1 so that many, if not all, of the then-existing SASI controllers were SCSI-1 compatible. In around 1980, NCR Corporation had been developing a competing interface standard by

1404-459: The earliest hard drives compatible with a floppy drive form factor . By 1983, Shugart Associates had shipped over 100,000 such drives. In the early 1980s, in order to avoid development and start-up costs, the company turned to Matsushita Communications Inc., a subsidiary of Panasonic Corporation (then known as Matsushita Electric Industrial Co., Ltd), for its half-height 5 + 1 ⁄ 4 -inch drives, sending that company on its way to becoming

1458-464: The enclosure using a specialized set of SCSI commands to access power, cooling, and other non-data characteristics. Shugart Associates Founded in 1973, Shugart Associates was purchased in 1977 by Xerox , which then exited the business in 1985 and 1986, selling the brand name and the 8-inch floppy product line (in March 1986) to Narlinger Group, which ultimately ceased operations circa 1991. After

1512-457: The engineers who worked on SASI left in 1981 to found host adapter maker Adaptec . Also in 1979, Shugart Associates introduced the SA-1000, a series of hard disk drives that kept as many mechanical, electrical and formatting similarities as possible with its floppy-drive counterparts. Their physical dimensions, including mounting holes, were the same as an 8-inch floppy drive, making them some of

1566-534: The faster serial SCSI (SAS) host adapters. The "small" reference in "small computer system interface" is historical; since the mid-1990s, SCSI has been available on even the largest of computer systems. Since its standardization in 1986, SCSI has been commonly used in the Amiga , Atari , Apple Macintosh and Sun Microsystems computer lines and PC server systems. Apple started using the less-expensive parallel ATA (PATA, also known as IDE ) for its low-end machines with

1620-407: The floppy disk drive, but Shugart wished to continue the original plan. Official company documents state that Shugart quit, but he himself claims that he was fired by the venture capitalists. Shugart went on with Finis Conner to found Shugart Technology in 1979, which was later renamed to Seagate Technology in response to a legal challenge by Xerox. The 5 + 1 ⁄ 4 -inch floppy disk drive

1674-429: The jumpers are typically located; the switch emulates the necessary jumpers. While there is no standard that makes this work, drive designers typically set up their jumper headers in a consistent format that matches the way that these switches implement. Setting the bootable (or first) hard disk to SCSI ID 0 is an accepted IT community recommendation. SCSI ID 2 is usually set aside for the floppy disk drive while SCSI ID 3

SASI - Misplaced Pages Continue

1728-531: The largest floppy drive manufacturer in the world. In 1985, in order to resolve an inventory accumulation and as part of its exit strategy, Xerox gave up Shugart's exclusive rights to the Matsushita half-height 5 + 1 ⁄ 4 -inch floppy drives. Shugart's eventual downfall came about partially as a result of the company failing to develop a reliable 80-track disk drive. In 1983 the company changed its name to Shugart Corporation. In late 1983, Shugart announced

1782-471: The later Blade 100 and 150 entry level systems and did not switch to contemporary SATA interface even with the introduction of the Blade 1500 in 2003 while the higher end Blade 2500 released at the same time used Ultra320 Parallel SCSI-3. Sun moved to SATA and SAS interfaces with their last UltraSPARC-III based workstations in 2006 with the entry level Ultra 25 and mid-range Ultra 45. Commodore included SCSI on

1836-403: The metal layer, forming a bubble. This deformation would cause a change in the intensity of the reflected light from a laser reading the disk, thus providing a means of data storage. Initial OEM pricing for the drive was given as $ 6,000 per unit in 250-unit quantities with disks priced about $ 266 each (UK price). Disks with capacities of up to 3 GB were reportedly being developed. Optimem

1890-638: The most commonly used being: Each device on the SCSI bus is assigned a unique SCSI identification number or ID. Devices may encompass multiple logical units, which are addressed by logical unit number (LUN). Simple devices have just one LUN, more complex devices may have multiple LUNs. A "direct access" (i.e. disk type) storage device consists of a number of logical blocks, addressed by Logical Block Address ( LBA ). A typical LBA equates to 512 bytes of storage. The usage of LBAs has evolved over time and so four different command variants are provided for reading and writing data. The Read(6) and Write(6) commands contain

1944-508: The name of BYSE. In the summer of 1981, NCR abandoned their in-house efforts in favor of pursuing SASI and improving on its design for their own computer systems. Fearing that their extension of the SASI standard would induce market confusion, however, NCR briefly cancelled their contract with Shugart. NCR's proposed improvements to the design of SCSI piqued the interest of Optimem, a subsidiary of Shugart, who requested that NCR and Shugart collaborate on

1998-571: The new acronym as "scuzzy" and that stuck. The NCR facility in Wichita, Kansas developed the industry's first SCSI controller chip, the NCR 5385, released in 1983. According to its developers, the chip worked the first time it was tested. A number of companies, such as Adaptec and Optimem, were early supporters of SCSI. By late 1990 at least 45 manufactures offered 251 models of parallel SCSI host adapters Today, such host adapters have largely been displaced by

2052-414: The operator choose the SCSI ID of the host adapter. Alternatively, the host adapter may come with software that must be installed on the host computer to configure the SCSI ID. The traditional SCSI ID for a host adapter is 7, as that ID has the highest priority during bus arbitration (even on a 16 bit bus). The SCSI ID of a device in a drive enclosure that has a back plane is set either by jumpers or by

2106-470: The parallel cable, and an asynchronous mode. The asynchronous mode is a classic request/acknowledge protocol, which allows systems with a slow bus or simple systems to also use SCSI devices. Faster synchronous modes are used more frequently. Internal parallel SCSI cables are usually ribbons , with two or more 50–, 68–, or 80–pin connectors attached. External cables are typically shielded (but may not be), with 50– or 68–pin connectors at each end, depending upon

2160-515: The presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements. The initial Parallel SCSI was most commonly used for hard disk drives and tape drives , but it can connect a wide range of other devices, including scanners and CD drives , although not all controllers can handle all devices. The ancestral SCSI standard, X3.131-1986, generally referred to as SCSI-1,

2214-589: The shift to serial interfaces is the clock skew issue of high-speed parallel interfaces, which makes the faster variants of parallel SCSI susceptible to problems caused by cabling and termination. The non-physical iSCSI preserves the basic SCSI paradigm , especially the command set, almost unchanged, through embedding of SCSI-3 over TCP/IP . Therefore, iSCSI uses logical connections instead of physical links and can run on top of any network supporting IP. The actual physical links are realized on lower network layers , independently from iSCSI. Predominantly, Ethernet

SASI - Misplaced Pages Continue

2268-409: The slot in the enclosure the device is installed into, depending on the model of the enclosure. In the latter case, each slot on the enclosure's back plane delivers control signals to the drive to select a unique SCSI ID. A SCSI enclosure without a back plane often has a switch for each drive to choose the drive's SCSI ID. The enclosure is packaged with connectors that must be plugged into the drive where

2322-785: The specific SCSI bus width supported. The 80–pin Single Connector Attachment (SCA) is typically used for hot-pluggable devices Fibre Channel can be used to transport SCSI information units, as defined by the Fibre Channel Protocol for SCSI (FCP). These connections are hot-pluggable and are usually implemented with optical fiber. Serial attached SCSI (SAS) uses a modified Serial ATA data and power cable. iSCSI (Internet Small Computer System Interface) usually uses Ethernet connectors and cables as its physical transport, but can run over any physical transport capable of transporting IP . The SCSI RDMA Protocol (SRP)

2376-518: The target returns a Check Condition in response to a command, the initiator usually then issues a SCSI Request Sense command in order to obtain a key code qualifier ( KCQ ) from the target. The Check Condition and Request Sense sequence involves a special SCSI protocol called a Contingent Allegiance Condition. There are four categories of SCSI commands: N (non-data), W (writing data from initiator to target), R (reading data), and B (bidirectional). There are about 60 different SCSI commands in total, with

2430-548: The title SASI . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=SASI&oldid=1064424496 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Shugart Associates System Interface Small Computer System Interface ( SCSI , / ˈ s k ʌ z i / SKUZ -ee )

2484-456: The traditional parallel SCSI bus and perform data transfer via serial communications using point-to-point links. Although much of the SCSI documentation talks about the parallel interface, all modern development efforts use serial interfaces. Serial interfaces have a number of advantages over parallel SCSI, including higher data rates, simplified cabling, longer reach, improved fault isolation and full-duplex capability. The primary reason for

2538-898: The unlimited scope of the (IP) network, the process is quite complicated. These discovery processes occur at power-on/initialization time and also if the bus topology changes later, for example if an extra device is added. SCSI has the CTL (Channel, Target or Physical Unit Number, Logical Unit Number) identification mechanism per host bus adapter , or the HCTL (HBA, Channel, PUN, LUN) identification mechanism, one host adapter may have more than one channels. While all SCSI controllers can work with read/write storage devices, i.e. disk and tape, some will not work with some other device types; older controllers are likely to be more limited, sometimes by their driver software, and more Device Types were added as SCSI evolved. Even CD-ROMs are not handled by all controllers. Device Type

2592-475: Was announced in December 1977 at $ 450. In 1979, Shugart Associates introduced the "Shugart Associates System Interface" (SASI) to the computing world; the interface subsequently evolved into SCSI (Small Computer System Interface). The first standard process completed in 1986 with ANSI standard X3.131-1986 (popularly known as SCSI-1 ) as the result. Larry Boucher led the SASI engineering team; he and several of

2646-546: Was discontinued. Initially, the SCSI Parallel Interface (SPI) was the only interface using the SCSI protocol. Its standardization started as a single-ended 8-bit bus in 1986, transferring up to 5 MB/s, and evolved into a low-voltage differential 16-bit bus capable of up to 320 MB/s. The last SPI-5 standard from 2003 also defined a 640 MB/s speed which failed to be realized. Parallel SCSI specifications include several synchronous transfer modes for

2700-592: Was introduced by Shugart in September 1976 as the Shugart SA-400 Minifloppy (Shugart's trademarked brand name ) at an OEM price of $ 390 for the drive and $ 45 for ten diskettes. The SA-400 and related models became the company's best selling products, with shipments of up to 4000 drives per day. The original SA-400 was single-sided with 35-tracks and used FM (single density) recording. It could be used on either hard - or soft-sector floppy controllers and

2754-769: Was published by the X3T9 technical committee of the American National Standards Institute (ANSI) in 1986. SCSI-2 was published in August 1990 as X3.T9.2/86-109, with further revisions in 1994 and subsequent adoption of a multitude of interfaces. Further refinements have resulted in improvements in performance and support for ever-increasing data storage capacity. SCSI is derived from the Shugart Associates System Interface (SASI), developed beginning 1979 and publicly disclosed in 1981. Larry Boucher

SECTION 50

#1732859228781

2808-454: Was sold in March 1986 to Narlinger, which promptly rebranded itself as Shugart Corporation Under the management of Narlinger, Shugart acquired several discontinued product lines such as Tandon's 8-inch floppy drives in 1986 and in 1988 bought the Optotech 5984 Write Once Read Many (WORM) drive and its manufacturing facility for less than US$ 4-million. In 1987, it acquired Kennedy Company ,

2862-414: Was sold to Cipher Data in 1986 who then discontinued operations in 1991. Shugart's operating losses in 1984 along with Xerox's own troubles led Xerox to conclude in 1985 that Shugart businesses were no longer strategically important, resulting in a decision to close down Shugart rather than invest in recovery. Most of Shugart's businesses were shut down afterwards; however its floppy disk drive business

2916-496: Was specified at 80.6 kB with a soft sectored controller. The drive became the basis of the disk system on the Radio Shack TRS-80 Model I , Apple II , and many other early microcomputers . Xerox announced acquisition of Shugart Associates in August 1977 and completed its purchase that December at a price of about $ 41 million. The 440 kilobyte SA450, a double-sided double-density 5¼-inch full height floppy disk drive

#780219