SCSI Interface
SCSI-Small Computer System Interface (Small Computer System Interface), is a kind of quite special interface bus, with multiple types of peripherals and communications. SCSI using ASPI (Advanced SCSI Programming Interface) standard software interface to drive and SCSI adapter installed inside the computer to communicate. SCSI interface is a widely used high-speed data transmission on the minicomputer technology. SCSI interface has a wide range of applications, multitasking, wide bandwidth, CPU occupancy rate is low, and hot and so on.
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SCSI interface is a basic overview of common interface SCSI interface, the type of SCSI device receiving an external small computer system interface storage device's interface to the basic classification has five categories the history of SCSI and IDE specific SCSI controller SCSI-2 increased the reliability of the launch of the Ultra2 SCSI (Fast-40) Ultra160 SCSI standard version check error correcting capability by increasing the reliability of the product enhances the connection type Explanation of terms Ultra320 SCSI SCSI ID and bus SCSI terminator future SCSI SCSI interface hard disk drive awareness of the different SCSI hard drive specifications: using hard disk on the server with the following four characteristics of the hard drive SCSI interface, SCSI interface hard disk performance SCSI interface to transfer the installation of ATA RAID disk array system
SCSI interfaces Basic Profile is a generic SCSI interface, SCSI bus interface can be connected on the SCSI host adapter and eight peripheral controllers, peripheral devices can include disk, tape, CD-ROM, rewritable optical drives,
nike air force one high, printers, scanners and communications equipment. SCSI is a multi-tasking interface with bus arbitration function. Hanging in a number of peripherals on the SCSI bus can work. Equal share SCSI devices on the bus. SCSI interface can be synchronous or asynchronous transmission of data, synchronous transfer rate up to 10MB / s, asynchronous transfer rate of up to 1.5MB / s. SCSI interface to an external device that receives the connection cable can be up to 6m. SCSI interface for optical storage products provide a powerful, flexible connections, it also provides a high performance, can have 7 or more drives connected to a SCSI adapter, the drawback is that the expensive price. SCSI interface drives need SCSI card together with the use of expensive, and the SCSI interface CD-ROM installation, setup is too much trouble, so the SCSI interface, IDE interface, CD-ROM drive far less widely used. SCSI interface, optical storage products, is used in more areas of expertise with special needs, household products, almost no use of such interface. [1] SCSI is a link to the host and peripheral interfaces that support, including disk drives, tape drives, optical drives, scanners, including a variety of devices. It consists of data operations SCSI controller, SCSI controller is equivalent to a small CPU, has its own command set and cache. To learn SCSI, you must first understand its type, the following is a STA (SCSI Trade Association, SCSI Trade Association) standard classification. SCSI type of comment:
SCSI interfaces
(1) point to point transmission bus length (2) SCSI, Ultra SCSI or Ultra2 SCSI is optional both (3) LVD (Low Voltage Differential, low scores differential) does not define its speed at 12 meters can maintain the normal transfer rate. If there is a bus device settings into a single end, the entire bus will switch to a single end. (4) there is no single definition of the end of its length (5) HVD (High Voltage Differential, score differential) does not define its speed (6) Ultra2, all are based on broadband high-speed transmission (Wide) mode. [2] that the above criteria, if a bit confused, in fact, for a new user, SCSI controller and data to know the type of line is more important than the interface type. In the SCSI bus, the controller can be considered a device, namely: the actual number of devices can be connected to support device = theoretical maximum number of -1. [3] Small Computer System Interface SCSI (Small Computer System Interface) simply called a literal translation from English to small computer system interface, which is a specially designed for small computer system interface mode storage unit, it is by the United States in 1979 Shijia Te (Shugart), Inc. (formerly Seagate) research and develop, and in 1986 received ANSI (American Standards Association) recognition. SCSI from discovery to now have ten years of history, it makes a lot of strong performance very strict performance requirements on the computer system. SCSI is a special kind of bus structure that can more than one device on the computer a dynamic division of operations, the system also required more appropriate allocation of tasks can be flexible, dynamic complete. This feature is beyond the reach of IDE devices. It is due to have these outstanding advantages of SCSI, SCSI can be made to occupy in the professional application of absolute dominance. In so many years in, SCSI, and no not rest, the face of powerful challenges IDE devices, SCSI is also constantly moving forward. [4] The basic classification of the storage device interface has five categories IDE, SCSI, USB, parallel port, serial port, parallel port and serial port which the
SCSI interfaces
speed is very slow, not worth mentioning, is the most important IDE, usb, SCSI. IDE (Integrated Drive Electronics, Integrated Drive Electronics), with its high-speed transmission and the usual price, was welcomed by ordinary users, while the usb device on the home of great potential newcomers, as SCSI (Small Computer System Interface, Small Computer System interface), speed, performance and stability is better than IDE, the price of course, but also much more expensive, mainly for server and workstation markets. In the past few years, IDE progress more quickly, Ultra DMA 33 launched less than two years, Ultra DMA 66 on the market. In fact, SCSI is not the development slower than IDE, but we are less exposed to its deep understanding of and nothing. SCSI standard was introduced in 1980, but up to now has not been uniform, the manufacturers are not the same as naming it, is to confuse the main reason. [3] SCSI and IDE SCSI SCSI in the face of new users, a question most often heard is: This is a difficult question to answer, which includes the performance, price, ease of use, scalability factors. From the performance, said, SCSI is certainly better than IDE, after all, there is a SCSI controller chip equivalent CPU, can handle most of the work, reducing the burden on the central processor (CPU usage). Launched at the same time the hard drive, SCSI product line speed, cache capacity and data transfer rate higher than the IDE system, than
SCSI interfaces
speed, IDE, but what better than SCSI. In terms of price, SCSI is a synonym for expensive, commercial-grade applications for, IDE Zeyi known for low prices, for desktop computers. Ease of use: using SCSI in the process, often occur and bus termination, SCSI ID settings error, leading to the failure does not recognize the hardware, IDE devices only the main and auxiliary of the points, only two data lines in the same equipment, as long as the respective is set to Master and Slave would not have conflict. Scalability: the ability to connect up to 15 SCSI devices is one of the advantages, and the standard PC, IDE interface, can connect up to 4 devices. Before buying a product, most notably taking into account the needs of users, with this, very easy to determine which product is more suitable, said only If you use a computer to play games, watch DVD, Internet, IDE hard drives have been able to meet your application, SCSI Quake 3 will increase only a few frames, absolutely worth it. If using a computer to video capture, video editing requires a lot of disk input / output work, that is your SCSI on the choice, do not buy in order to save some money Oh IDE, otherwise it will outweigh the benefits. History of the development of specialized applications in the system SCSI controller must have a dedicated SCSI SCSI controller, which is a SCSI controller card to support
SCSI interfaces
SCSI device support, which is different IDE hard drives. There is a SCSI controller in the CPU chip equivalent, its control of SCSI devices, capable of handling most of the work, reducing the burden on the central processor (CPU usage). In the same period of the hard disk, SCSI hard disk speed, cache size, data transfer rate higher than the IDE drives, so more is used in commercial areas. SCSI was first Shugart 1979 by the United States, Inc. (formerly Seagate) formulated in 1986, won the ANSI (American National Standards Institute) is recognized as SASI (Shugart Associates System Interface Shijia Te Joint System Interface), which is the SCSI -1. SCSI-1 is the first SCSI standard supports synchronous and asynchronous SCSI peripherals; use 8-bit channel width; up to seven devices allowed to connect; asynchronous transmission when the frequency is 3MB / S, the frequency of simultaneous transmission of 5MB / s ; support WORM peripherals. It uses 25-pin interface, so the connection to the SCSI card (SCSI card interface for 50-pin) on, you must have an internal 25-pin interface cable for 50. This kind of interface has basically been eliminated, in the very old equipment or individual can see the scanner device. Increase the reliability of SCSI-2 SCSI-2 has been called the Fast SCSI, SCSI-1 it has made on the basis of greatly improved, also added a reliable
SCSI interfaces
, data transmission rate was increased to 10MB / s, still using 8-bit parallel data transfer, or up to 7 devices. Subsequently been improved, launched a 16-bit parallel data transfer to support the WIDE-SCSI-2 (broadband) and FAST-WIDE-SCSI-2 (fast broadband), which WIDE-SCSI-2 data transfer rate has not increased, just use 16-bit transmission; and FAST-WIDE-SCSI-2 is the data transfer rate to 20MB / s. SCSI-3 standard version is launched in 1995, also commonly called Ultra SCSI, the synchronous data transfer rate of 20MB / s. If you use 16-bit Wide mode of transmission, the data transfer rate can also be increased to 40MB / s. The maximum allowed length of the interface cable is 1.5 meters. Introduced Ultra2 SCSI (Fast-40) standard version launched in 1997 Ultra2 SCSI (Fast-40) standard version, which is still 8-bit wide data path, but the use of LVD (Low Voltage Differential, low differential) transmission mode, the transmission rate of 40MB / s, the interface cable to allow up to 12 meters, greatly increasing the flexibility of the equipment to support 15 devices simultaneously articulated. Then it launched a WIDE ULTRA 2 SCSI interface standard, which uses 16-bit data path bandwidth, maximum transfer rate of up to 80MB / S, the interface cable to allow up to 12 meters, also supports 15 devices mounted at the same time, greatly increasing equipment flexibility. LVD can use the lower voltage, so you can program the differential driver and receiver integrated into the hard disk of the onboard SCSI controller. Need to use the old SCSI independent,
nike air force 1 high, high-voltage power devices. LVD uses the low power
SCSI interfaces
voltage and low current device, so the differential transceivers can be integrated in the drive's onboard SCSI controller, no longer need a separate external high-voltage high-cost differential components. LVD drives can be multi-mode conversion, when all conditions are met, the drive to work in the LVD mode; the contrary, if not all conditions are met, the hard disk will be reduced to single-ended mode. LVD hard drive to increase the bandwidth for the server environment, it means better performance. Server environment are required to have rapid response, must be able to carry out random access and large queues operations workload. When you use such as CAD, CAM, digital video, and various other software RAID, when the effect of increasing the bandwidth can be immediate, information can be transmitted quickly and easily. Ultra160 SCSI Ultra160 SCSI, also known as Ultra3 SCSI LVD, SCSI is a mature interface standard, is in the Ul
SCSI interfaces
tra2 SCSI, based on developed, using a double-conversion clock control, cyclic redundancy check and the name recognition and other new technologies. Double conversion clock control interface clock frequency without increasing the case of the data transfer rate has doubled, which is Ultral60 SCSI interface, a substantial increase in the key rate. Use of Ultra160 SCSI, simple and easy to implement, low risk. In enhancing the reliability and manageability while, Ultra160 SCSI Ultra2 SCSI transfer rate of 2 times to 160MB / s. Ultra160 SCSI interface, has the following characteristics: Ultra2, and Ultra160 devices can be installed on a bus, Ultra160 device performance will not decline; enhanced by increasing the error correction check the reliability of product performance and higher reliability monitoring interface transfer rate capacity; for a single device cable length up to 25 meters for two or more devices of cable lengths up to 12 meters; in a channel to support up to 15 SCSI devices; Ultra320 SCSI Ultra320 SCSI, also known as Ultra4 SCSI LVD, SCSI interface, is relatively new standard. Ultra320
SCSI interfaces
SCSI Ultra160 SCSI is based on the developed, Ultra160 SCSI's advantage to continue to develop, Ultra160 SCSI's three key technologies, namely double-conversion clock control, cyclic redundancy check and domain name recognition, have been retained. Before the SCSI interface standard in the past, SCSI interface supports two transmission modes: asynchronous and synchronous. Ultra320 SCSI transfer mode introduced pacing, in which transmission mode, the simplified data clock logic, the Ultra320 SCSI's high transfer speed possible. Ultra320 SCSI transfer rate up to 320MB / s. Ultra320 SCSI has the following characteristics: 1, double data rate data transmission, data transmission speed than doubling Ultra160 SCSI; 2, the group of the SCSI, support group agreement; 3, quick arbitration and selection, greatly improving the utilization of the bus rate; 4, read and write data streams, to minimize the overhead of data transmission; 5, flow control, improve bus utilization. The development process, each generation of SCSI products, product performance than doubling the previous generation. New generation of products, Ultra320 SCSI, continue to uphold this tradition by the Ultra160 SCSI bandwidth of 160Mbps up to 320Mbps. Ultra320 SCSI protocol changes needed to reduce the command / state spending to maximize the use of high bandwidth advantage. Therefore, Ultra320 SCSI also introduced several new features to support high-speed and reliable data transmission. These new features include physical / signal enhancement and protocol enhancements. Physics / signal enhancement Ultra320 SCSI bus speeds higher signal on the need for enhanced to ensure data can be used in the previous generations of products similar to cable length and reliable manner. Ultra320 SCSI signal enhancement, including twice the transmission speed, pacing (paced) transfer, training mode and drive pre-compensation. Twice the transfer speed: Ultra320 SCSI data transfer rate doubled to 320Mbps while, Ultra320 SCSI Ultra160 SCSI to continue to use the clock in the launch of bilateral mechanisms, but the clock speed doubled, to 80MHz. Improved performance in bulk data transfer, or a single bus to connect multiple devices in the system was particularly significant. [5] Connection type SCSI connectors are divided into internal and external both. Built-in data line shape and the same IDE cable, only slightly different pin counts and specifications, mainly used to connect CD-ROM and hard disk, 40-pin IDE cable has 40 conductors, 40 pins, 80 wire ATA66, SCSI internal is divided into 50-pin, 68-pin and 80 pin. As for the external SCSI cable, there are several specifications, they are not the same density, do not mistake. Apple SCSI, 25 pin, divided into two rows, 8 bits, commonly used in older Mac machines and Sun workstations. Sun Microsystem's DD-50SA, 50-pin, divided into three rows. SCSI-2, 50 needle, divided into two rows, 8 bits. Centronics, 50 pin, is divided into two rows, 8 bits, a bit like a parallel port, it can be the largest number of connected devices. SCA, 80-pin, divided into two rows. SCSI-3, and Wide SCSI-2, 68 needle, divided into two rows, 16-bit. Old DEC single-ended SCSI with 68-pin high-density interfaces. SCSI Connectors / SCSI interface type and length of the DB-25, Male External DB-25, male external interface to DB-25, Female External DB-25, female external interfaces Low-Density, 50-pin, Male External 50-pin low density Male External Interface (6.5cm) Low-Density, 50-pin, Female External low-density 50-pin female External Interface High-Density, 50-pin, Male External high-density 50-pin male external interfaces (3.3cm) High- Density, 50-pin, Female External high-density 50-pin female external interfaces Low-Density, 50-pin, Male Internal low-density 50-pin male built-in interface (7.1cm) Low-Density,
air force one shoes, 50-pin, Female Internal low-density Built-in 50-pin female excuses High-Density, 68-pin, Male External 68-pin male high density external interfaces (4.5cm) High-Density, 68-pin, Female External 68-pin female high-density external interface, High-Density, 68-pin,
air force one high, Male Internal 68-pin male high density built-in interface (4.5cm) High-Density, 68-pin, Female Internal 68-pin female high-density built-in interface VHDCI, 68-pin, Male External very high-density 68-pin male External Interface (3.2cm) VHDCI, 68-pin, Female External very high-density 68-pin female SCSI External Interface Specification common terms to explain some standard terminology to explain: Single Ended (single end): Many older devices are single-ended equipment, they are limited to SCSI-1 protocol 6 meters length. NOTE: This distance includes the distance between the cable inside the device. Differential (points differential): SCSI bus and devices can make use of it along the long transmission distance, an additional line of maximum length of 25 meters. The disadvantage is not compatible with single-end equipment. Fast SCSI: the SCSI bus speed of the first generation increased from 5MHz to 10MHz, the theoretical data transfer rate is doubled to 10MB / sec. Ultra SCSI: the SCSI bus speed of the first generation increased from 5MHz to 20MHz, the theoretical data transfer rate is doubled to 20MB / sec. Wide SCSI: It depends on the second or 68-pin data cable data cable to increase the performance of the bus, the data bit width is 16 or 32 bits, to improve the performance of traditional SCSI or 4 times to 2 times. Wide Ultra SCSI: 68-pin data cable to use the bus performance to 40MB / sec. The above description alone, it can not accurately determine the type of a SCSI bus, you must also understand its bus width, bus speed, data types, and additional command line set to achieve the goal. SCSI ID and SCSI bus terminator believe that many users have this experience, plug in the device, how the operating system does not recognize, then check the bus, only to find that there is no set end and ID. ID (identify) SCSI device in the SCSI bus as a unique identifier, and definitely not repeat, selectable from 0 to 15, SCSI host controller usually takes id 7, that is, we can use the ID number on the device A total of 15. Bus termination, SCSI host controller device can tell where the end of the entire bus, and issued a reflected signal to the controller, you must be a physical terminal end of the two signals in order to use SCSI bus. A common mistake is to set the ID number to the end of the highest or lowest, rather than the physical end of the SCSI setting on the device. In fact, SCSI devices to connect to form always in chains, according to the order will be able to tell which one is the end of the device. End of three ways: from the end of the device, and the physical bus terminator from the end of the cable. Most new SCSI device has since the end of the jumper, as long as the non-end equipment from the end of the jumper set to OFF to avoid conflict; physical bus terminator is a hardware connection, is divided into two active-and passive species, active use of voltage regulators to operate, use of passive energy signal on the bus operation, passive is more accurate than proactive; since the end of the cable can replace the physical bus terminator, is also a hardware, its price very expensive, commonly used in the two hosts connected to the same physical device, such as: two servers accessing the same physical SCSI hard disk. By checking the SCSI ID and bus terminators, we can find solutions to the phenomenon of most conflicts, it is SCSI device users must pay attention to the point. SCSI SCSI is the future of a constantly advancing technology, recently joined the specifications of Fibre Channel SCSI, IEEE 1394 (Firewire, Firewire) and SCSI 3 (160MB / s), about the birth of a SCSI 4 (320MB / s) and SCSI 5 (640MB / s). Starting from the SCSI 3, SCSI can quickly improve performance as needed, and has near-perfect backward compatibility, protecting the user's investment. With the rising rate of addition, SCSI also begun to focus on ease of use, the use of CAM (Common Access Model, public access model) in the number of SCSI command set and the program adjusted by adding a control layer between, so that programming is more SCSI for the convenience. I firmly believe that scientific progress will bring a SCSI and a technical peak, the future will become more expensive SCSI certainly easier to use. [3] real SCSI standard appeared in 1986, which is commonly referred to as SCSI-1 standard. Look to the technical standards, SCSI-1 can be said to be very backward, and it sent the signal frequency is only 5MHz, and each can only send 8 bits of data, the maximum transfer rate that is only 5MB / s. SCSI-1 support for SE (Single-Ended) and high-voltage differential signaling (HVD), although the connection with the HVD can transmit signals up to 25 meters, but its high cost, generally only to send the signal SE, the connection maximum length is 6 meters. Compatibility with SCSI-1 standard is not good, or even a lot of equipment can not be used together, can only take up to 7 peripherals. Continue to introduce the Ultra320 SCSI, or SCSI-3 that under the standard design, Ultra320 SCSI inherited the previous generation of Ultra160 SCSI technology, but quickly doubled to 320MB / s, which is mainly to further improve the clock frequency to 80MHz, but still use 16-bit bus to transmit data. LVD technology since the emergence of the length of the data line by the bus frequency effects have been minimal. How will the next SCSI technology development, we believe the international data transmission rate will be further increased, the width of the bus will increase. In fact, 320MB / s for the average server is enough. [6] SCSI interface hard disk drives that use SCSI interface, SCSI hard drives. It is because of good performance, high stability, it is widely used on the server. At the same time its price is also expensive, precisely because it is expensive, so rarely seen in ordinary PC, traces of it. Speaking of SCSI interface, SCSI hard drives must be mentioned, SCSI is the Small Computer System Interface (Small Computer System Interface) is an abbreviation, use 50-pin interface, hard disk interface and the general appearance is somewhat similar. Ordinary IDE hard disk drives and SCSI has many advantages compared: the interface speed, and because mainly for servers, so the performance of the hard disk itself is relatively high, fast hard drive speed, cache capacity, CPU occupancy rate, scalability is much better than IDE hard disk, and supports hot swap. SCSI hard disk manufacturers now produce mainly: Seagate (Seagate), Quantum (Quantum), IBM and WD (Western Digital). More expensive SCSI drives, SCSI hard drives same capacity than the IDE hard drive of your price more than 80%, so the SCSI hard drive is mainly used in high-end servers and high-end workstations. SCSI hard drives has always been considered to be expensive and out of reach of the storage devices, IDE hard drives not only a lot higher than the price itself, but also want to use the IDE hard disk, you must also select the SCSI interface card. So in such conditions, the general computer user would prefer to use IDE interface hard disk. IDE hard drive, while having the advantage of low prices, but still no match for the powerful speed SCSI hard drives; coupled with SCSI interface is a Many people think that simply installing SCSI hard drives large projects, like IDE hard drives, as long as the set has (Master or Slave) can be used. In fact, he is also not as complex, after all, the installation and set more stringent, the more we can provide a stable operating environment. [7] recognize SCSI SCSI hard disk every time when they issued new specifications, SCSI hard drive and followed the same time support the new specifications, the SCSI hard drive makes the SCSI peripherals has become a leader. As hard drive technology has developed quite mature, so the interface on the SCSI hard drive with, always able to keep up with the times; Furthermore, the hard disk is very important to the computer equipment, but he is not missing. Actually, all of the hard drive all look alike, but because of the different SCSI specifications, and make some appearance, there are some differences. SCSI hard drives of different sizes: The 68-Pins Wide SCSI pin, you can use the channel width of 16-bit data transfer. With 60-Pins Narrow SCSI pin, only to 8-bit channel width of the transmission of data. Jimper (jumper) settings, mainly used to adjust the drive's ID, termination resistance switch. SCSI hard disk is very expensive computer peripheral equipment, carrying, absolutely you should be very careful. As the current speed SCSI hard drives are quite high (about 7200RPM ~ 10,000 RPM), so either as external or built-in way way to install the hard drive, with good heat dissipation are required environment. Personal computers are used on most hard disk drives of this type. Another hard drive is a SCSI hard disk of the (SCSI or Small Computer System Interface Small Computer System Interface), because of its good performance, so common on the server hard drives are the use of such products, but it's also very expensive, so in general PC, you can not see a trace of SCSI. Hard disk with the PC, compared to normal. Used the server has the following four characteristics of a hard disk, hard disk speed, server speed quickly, can reach 7200 or 10,000 rpm per minute, or even higher; also equipped with large (usually 2MB or 4MB) of the write-back caching; average access time is short; external transfer rate and a higher internal transfer rate, the use of Ultra Wide SCSI, Ultra2 Wide SCSI, Ultra160 SCSI, Ultra320 SCSI standards such as SCSI hard disk, per second data transfer rate up to 40MB, 80MB, 160MB, 320MB. 2, high reliability, because the server is almost hard to function 24 hours a day, under a huge workload. Can be said that the hard disk if a problem, the consequences could be disastrous. So now the hard drive are using SMART Technology (Self Monitoring, Analysis and Reporting Technology), while hard drive manufacturers have adopted their own unique advanced technology to ensure data security. In order to avoid unexpected losses, the server hard drive in general can withstand the impact of 300G to 1000G. 3, using the SCSI interface, the majority of multiple servers using the data throughput, CPU share of low SCSI hard drives. SCSI interface, SCSI hard drives must be used, and some server board integrated SCSI interface, and some have a dedicated SCSI interface, security card, a SCSI interface card can connect seven SCSI devices, which is IDE interface can not be compared. 4, supports hot hot (Hot Swap) supported by the server hard drives are installed, it can be kept on the server machine case, pull out or insert a disk, the operating system automatically recognizes the hard disk changes. The technology for servers running 24 hours a day, it is very necessary. SCSI card caused the system crash when starting to solve this problem and the main motherboard BIOS may be caused by the conflict. Please check the latest motherboard does not use BIOS. Recommend that you use the latest motherboard BIOS to resolve potential conflicts or BIOS of the bug problem. It can also be plugged into a different PCI card slot up to avoid a possible IRQ conflict. If and when no device is connected to the card, the system starts normally; But when device is connected, the system crashes, please note the following: * Make sure the end of the device in the SCSI chain has been correctly ended. * Note that all devices are using a different SCSI ID · upgrade to the latest motherboard BIOS · Check the system resource conflicts: BIOS, Port (port), and interrupt (interrupt) address for a different SCSI cable you can also When the system starts to change SCSI card BIOS settings. At boot time, when the card has prompted the message, press Ctrl + A, enter the SCSISelect, then select Configure / View Host Adapter Settings, then select the following set 1. Initiate Sync Negotiation = ; The lowest setting available SCSI interface hard disk performance hard drive speed is often overlooked. Subject to the limitations of IDE interface, IDE hard drives have tended to increase the speed limit. SCSI hard drive now has reached a maximum speed of 15,000 rev / min, the average seek time at 5ms or so, the key is the SCSI disk greatly reduce the CPU's share. 7200 SCSI disk is now the price has reached an acceptable level, if economic conditions permit, use SCSI disk will effectively improve the overall performance computers. And USB, IEEE1394 interface, such as different, SCSI (Small Computer System Interface) standard appears very early, it makes the computer system through a SCSI interface card to the host's identity and a variety of peripherals connected. SCSI devices including hard drives, CD drives, tape,
air force one low, scanner and many other common peripherals. Peripherals through a special cable and termination resistors connected with the SCSI adapter card. SCSI cables to SCSI devices in series into a daisy chain. SCSI bus supports fast data transfer. SCSI devices usually have a different 8-bit or 16-bit SCSI transfer bus. SCSI host adapter usually uses DMA (direct memory access) channel to transfer data to memory. This means that the help does not require the host CPU, SCSI adapter to connect the data to memory, thus greatly reducing the share of peripherals on the CPU. [8] SCSI interface hard disk to install most of the hard drives bought from the market are built-in hard drive, only some of the vendors back to the SCSI hard drives with higher external box to sell, this way they become a ready-made external hard disk. If you think your computer case with good heat dissipation, but also free space, the money can be left external box, connected directly to the SCSI hard drive in the computer chassis. Installation To install the internal hard drive to the chassis, need some tools to help, at least for the following difference: 1, Phillips screwdriver: hard drive, SCSI interface card will need to use screws to fix the chassis, then must use Phillips screwdriver to complete these tasks. 2, needle nose pliers: to be removed with needle nose pliers, insert the hard drive Jumper, to set the hard disk ID, the terminal resistance switching and so on. Supply of all packages: the built-in way to install the SCSI hard drive, accessories for the following groups: 1, SCSI hard drives: This is of course the main character is absolutely indispensable. 2, SCSI interface card: Unless your motherboard has built-in SCSI interface, or absolutely have to prepare a SCSI interface card; addition SCSI interface card and hard drive with the also very important to follow the standard SCSI hard drive to use with. If you are using Fast SCSI interface card to go with Ultra-Wide SCSI hard drive, although no problem in the use (can be converted first), but the speed and channel width would decrease long-Fast SCSI standards. 3, SCSI cable: SCSI internal cable into 50-Pin Single-Ended ,68-Pin Single-Ended ,68-Pin LVD three, please clear understanding of their own which must be used with SCSI hard drive cable. 4, screws: to fix the hard disk and SCSI interface card, the two specifications may not be used as Oh! The installation steps: Install the SCSI hard drive, you first look at the entire process: Hard Disk Jumper Settings → → fixed interface cards and hard disk to cable to connect the hard disk drive and interface cards connected to the power 1 → adjust the SCSI hard disk Jumper (Jumper): Jumper on the hard disk can be used to set the SCSI ID, termination resistors, Parity Check and more. 2, the SCSI interface card plugged into the motherboard: the SCSI interface card plugged into the correct slot on the motherboard, and confirm the correct insertion; Phillips screwdriver and screws and then use the interface card is secured. 3, fixed hard drive: The hard disk on the bracket to the chassis. 4, the connection cable: The cable to connect SCSI interface card and hard disk ,68-Pins Wide SCSI connectors for special trapezoid,
nike air force 1, so the connection does not reverse the problems. If the installation is Narrow (50-Pin) hard drive, please note that 50-Pin cable to align the red part of the hard disk or interface card of the Pin-1. 5, the holder back into the chassis and connected to the power: To determine whether the holder of the hard disk is installed, and then plug the power cord in the hard disk. So far, the installation of the hardware in general has no problem, you can check a SCSI interface card, cable, power cord is connected properly; If everything all correct, you can turn on the console and see the display screen on the SCSI BIOS whether these units can be found in SCSI hard drive models. SCSI BIOS startup screen appears, locate the SCSI hard drives that the hardware is installed correctly! External SCSI hard drive external external hard drive will have many benefits, such as: 1, do not turn off the power when used in hard disk, reducing unnecessary disk workload. 2, demolition, easy installation, no need to open the host chassis. 3, ID can directly switch on the chassis, not on the hard drive plug Jumper. 4, external sound box can be equipped with three independent heating system, to drive a better working environment for heat dissipation. SCSI drives are generally more common external box, its external interfaces for the low-density or high-density 50-Pin 50-Pin to SCSI connector, an external box within the 50-Pin Zeyi the internal cable to connect the hard disk. As for the Ultra Wide SCSI hard drive is more rare special external box, its external interface is 68-PinWide connector. Internal Zeyi trapezoidal 68-Pin Wide SCSI internal cable connected to the hard disk. The latest Ultra2 Wide SCSI LVD hard drive, due to the higher requirements of connecting cable, twisted pair plus a special design, so both the external box external cable or SCSI cable must be redesigned, still do not see this product. SCSI hard disk to install two or more if more than two SCSI hard drives, can be used to install the following permutations: 1, hard drives are built with a SCSI interface card on the same: general SCSI interface card attached to the built-in cable can only be connected