Hard Disk Interface

From: Baidu

The hard disk interface is a connecting part between the hard disk and the host system, which transmits data between the hard disk cache and the host memory. The different hard disk interface determines the connection speed between the hard disk and the computer, in the whole system, the quality of the hard disk interface directly affects the program running speed and performance.OverviewFrom the overall point of view, the hard disk interface is divided into IDE, SATA, SCSI and Fibre Channel Four, IDE interface hard disk for home products, but also partly applied to the server, SCSI interface of the hard disk is mainly used in the server market, and Fibre Channel only in high-end servers, the price is expensive. SATA is a new type of hard disk interface, and is in the market-wide stage, and has a broad prospect in the home market. In the IDE and SCSI categories, you can also distinguish a variety of specific interface types, and each have different technical specifications, with different transmission speed, such as ATA100 and sata;ultra160 SCSI and Ultra320 SCSI are representative of a specific hard disk interface, Their speed difference is also greater.
　　 IDE
The IDE's English is all called "Integrated Drive Electronics", or "Electronic integrated Drive", which is meant to be the hard drive that integrates the hard disk controller and the disk body. The integration of the disk and the controller reduces the number and length of cables to the hard drive interface, enhances the reliability of the data transmission, and makes it easier to make the hard drive because the hard drive manufacturer does not need to worry about whether its hard drive is compatible with the controller produced by other manufacturers. For users, hard disk installation is also more convenient. IDE this interface technology from the birth has been constantly developing, performance has been continuously improved, its low-cost, compatible with the characteristics of strong, for its other types of hard disk can not replace the status.
The IDE represents a type of hard disk, but in practical applications, it is also customary to use the IDE to address the earliest IDE type hard disk ATA-1, a type of interface that has been eliminated with the development of interface technology and later branched out into more types of hard disk interfaces, such as ATA, Ultra ATA, Interfaces such as DMA, Ultra DMA, and so on are part of the IDE hard disk.
　　 SCSI
The English of SCSI is all called "Small Computer system Interface" (Small computer system interface), is a completely different interface with IDE (ATA), the IDE interface is standard interface of normal PC, and SCSI is not the interface specially designed for hard disk, is a kind of high-speed data transmission technology which is widely used in small machine. SCSI interface has a wide range of applications, multitasking, large bandwidth, low CPU usage, as well as hot Plug and so on, but the high price makes it difficult as the IDE hard drive, so the SCSI hard disk is mainly used in high-end servers and high-end workstations.
　　 Fibre Channel
The English spelling of Fibre Channel is fibre Channel, same as the Scis interface. Fibre Channel was not originally designed for hard disk design and development of interface technology, is designed for the network system, but with the storage system on the speed of the need to gradually apply to the hard disk system. The Fibre Channel hard disk is developed to improve the speed and flexibility of the multi-disk storage system, and its appearance greatly improves the communication speed of the multi-disk system. The main characteristics of Fibre Channel are: hot-pluggable, high-speed bandwidth, remote connection, large number of connected devices.
Fibre Channel is designed for the environment of a multi-disk system such as a server, which can meet the requirements of high data transmission rates for high-end workstations, servers, mass storage subnets, and peripherals through hubs, switches and point-to-point connections for two-way, serial data communication systems.
　　 SATA
The use of SATA (serial ATA) port hard disk is also called serial hard disk, is the future of PC hard drive trend. In the 2001, the Serial ATA Commission, made up of Intel, APT, Dell, IBM, Seagate and Serial, officially established the ATA 1.0 specification, and in 2002, although serial ATA related equipment was not officially listed, serial The ATA Commission has preempted the Serial ATA 2.0 specification. Serial ATA uses serial connection, the Serial ATA bus uses the embedded clock signal, has the stronger error correcting ability, compared to the past its biggest difference is can carry on the transmission instruction (not only the data) to examine, if discovers the error will automatically correct, this greatly enhances the data transmission reliability. The serial interface also has the advantages of simple structure and hot-swappable support.
Serial disk is a kind of new type of hard disk interface which is completely different from parallel ATA, which is well-known for transmitting data by serial way. Compared to parallel ATA, it has a lot of advantages. First, the Serial ATA transmits data serially, and only 1 bits of data are transmitted at a time. This reduces the number of pins in the SATA connector, making the number of cables less and more efficient. In fact, serial ATA can do all of its work with only four pins, which are used to connect cables, connect ground wires, send data and receive data, and such architectures can reduce system energy consumption and reduce system complexity. Second, Serial ATA has a higher starting point and greater development potential, and Serial ATA 1.0 defines a data-transfer rate of up to 150mb/s, which is higher than the most recent parallel ATA (that is, ata/133) to achieve the highest data transmission rate of 133MB/S, while Serial ATA 2.0 of the data transmission rate will reach 300mb/s, the final SATA will achieve 600mb/s maximum data transmission rate.
　　 Sataii Interface
SATA II was developed on the basis of SATA, and its main feature was that the external transmission rate was further increased from SATA 1.5Gbps (150mb/sec) to 3Gbps (300MB/SEC), in addition to NCQ (Native Command Queuing , native command queue), Port multiplier, staggered start (staggered spin-up) and a series of technical features. Pure external transmission rate of 3Gbps is not true SATA II.
The key technology of SATA II is the external transmission rate and NCQ technology of 3Gbps. NCQ technology can optimize the instruction execution order of the hard disk, avoid moving the head to read and write the hard disk in the same order as the traditional hard disk, and in contrast, it will sort it after receiving the command, and the head of the sort will be addressed in an efficient order. So as to avoid the loss caused by repeated movement of the head, prolong the hard life. In addition, not all SATA drives can use the NCQ technology, in addition to the hard disk itself to support NCQ, also requires the motherboard chipset SATA controller support NCQ. In addition, the NCQ technology does not support the FAT file system, and only the NTFS file system is supported.
Due to the confusion of the SATA equipment market, many SATA device providers abuse the "SATA II" in marketing, for example, some of the so-called "SATA II" hard drives only support 3Gbps and do not support NCQ, Some 1.5Gbps-only hard drives support NCQ, so the Sata-io (serial ATA International organization,sata International Organization, the original SATA workgroup) led by Seagate (Seagate) The SATA 2.5 specification is also announced, featuring most of the features of the original SATA II-from 3Gbps and NCQ to staggered-boot (staggered spin-up), hot-swappable (thermal Plug), Port-multiplexing (ports multiplier) As well as the newer eSATA (External SATA, external SATA interface) and more.
It is noteworthy that some of the older motherboards that support only 1.5Gbps-only South bridge chips (such as via VT8237 and Nvidia NForce2 MCP-R/MCP-GB) may be unable to find a hard drive or blue screen when using SATA II drives. Most hard drives, however, set a speed-selection jumper on the hard drive to force a 1.5Gbps or 3Gbps mode of operation (a handful of hard disk vendors are set up by the appropriate tool software), as long as the hard drive is forced to 1.5gbps,sata II hard disks can still be used normally on old motherboards.
SATA hard drives typically need to install the driver provided by the motherboard chipset manufacturer when setting RAID mode, but there are also a few older SATA RAID controllers that can build raid without having to load the driver on certain versions of the Windows XP system that are in the latest patches.Development HistoryToday, as technology matures, more and more motherboards and hard disks are starting to support SATA (Serial ATA), and SATA interfaces are gradually replacing the traditional pata (parallel ATA) trend.
What is the difference between SATA and PATA in transmission mode, and what are the advantages of SATA relative Pata? This is the topic that this article needs to discuss.
　　 What is parallel ATA
ATA is actually an interface standard for IDE devices, and most hard drives, optical drives, floppy disks, and so on are using ATA interfaces. For example, the majority of friends now use parallel ATA interface of the hard disk, it should be 80-pin line of the interface is more familiar with it? Usually we talk about the hard disk interface, we have to mention what ultra-ata/100, ultra-ata/133, what does this mean? This tells us that the maximum transfer rate of the hard disk interface is 100mb/s and 133mb/s, and the hard drive is in parallel to transmit data, so we also call this kind of hard disk parallel ATA.
　　 What is Serial ATA
Serial ATA full name is Serial ATA, which is a new interface standard. The main difference with parallel ATA is the way it is transmitted. It is different from parallel transmission, it has only two pairs of data lines, using point-to-point transmission, in order to transfer the data in a higher speed than the parallel transmission. The current Serial ATA interface transfer rate is 150mb/s, and this value will grow rapidly.
　　 the difference between Serial ATA and parallel ATA transmissions
For example, A and B teams are moving packages in a game, and a represents a parallel ata,b for serial ATA.
At the beginning of the game, a dispatched 40 men to carry the parcel, and B sent only a lorry to carry it. In a back and forth they carry the same number of parcels, we can be very clear that the final result, of course, is the Van B team to carry the package, because the speed of the truck faster than people walk a lot more. Similarly, serial transmissions are similar to the rate of parallel transmission.
Back in reality, the parallel ATA interface now uses a 16-bit two-way bus that can transmit 4 bytes of data during 1 data transfer cycles, while the 8-bit bus used by Serial ATA can transmit 1 bytes per clock cycle.
These two modes of transmission, in addition to the transmission speed of each clock cycle is not the same, there is also a fundamental difference in the mode of transmission, where the serial ATA data is transmitted by one packet after another, while parallel ATA transmits several packets at a time, although more data is transferred by parallel ATA on the surface of a cycle. But let's not forget that serial ATA clock frequency is much higher than the parallel clock frequency, that is, the number of times in a unit time to carry out data transmission more, so the transmission rate of Serial ATA is higher than the transmission rate of parallel ATA, and there is more room for improvement in the future.
　　 Why should I use a Serial ATA interface?
The answer is simple, of course, to get a higher rate of data transfer. With the increasing of the data transmission rate of the current equipment requirement, the working frequency of the interface is more and more high, the parallel ATA interface gradually exposes some design "mishap", among which the most fatal is the signal interference of parallel circuits. Because the traditional parallel ATA uses the parallel bus transmission data, must request the data synchronization on each line, if the data cannot synchronize, can appear repeatedly reads the data, causes the performance to descend, even causes the reading data to be unstable.
And the use of line design data line, it is the data can not be read faster "culprit." Because of the high speed signal being transmitted, a weak electromagnetic field is generated around each cable, and then affect the data transmission in other data lines, but also because of the length of the cable and voltage changes and constantly changing, with the bus frequency, the strength of the magnetic field is more and more large, the impact of signal interference is more and more obvious.
Theoretically, the working frequency of serial transmission can be increased infinitely, and serial ATA is to improve the interface transmission rate by increasing the working frequency. As a result, serial ATA can achieve a higher transmission rate, while parallel ATA is difficult to achieve such a high transmission rate until the crosstalk problem is effectively resolved.
Parallel ATA interface is restricted by its design in bus frequency. And can not blindly upgrade, and as the data transfer rate of higher requirements, the current fastest parallel ATA interface ATA133 frequency of 33MHz, this has almost reached the limit of the parallel interface, and then continue to transform the line has not been realistic. So it is imperative to launch a new interface.
Besides the high transmission rate, what are the advantages of SATA?
1. More reliable data
In the verification aspect, the parallel ATA bus is just a simple CRC check, once the receiver found that the data transmission problem, they will discard them, and then request a postback, if the data signal interference too large, it will seriously affect the performance of the hard disk.
The Serial ATA can improve the reliability of the bus by CRC checking the command and CRC checking the data.
2. Easy connection
In the data line, parallel ATA with 80-pin line, Serial ATA due to the use of point-to-point way to transmit data, so only need 4 lines to complete the send and receive function, plus the other three ground, a total of only 7 physical connection to meet the needs of data transmission. Due to the low transmission data lines, SATA in the physical circuit of the electrical performance of the interference greatly reduced, which also ensures the future disk transmission rate further upgrade.
Compared to parallel ATA, the data cable of Serial ATA is finer, which makes the wiring inside the chassis easier to organize, helps the airflow inside the chassis, and makes the cooling inside the chassis better. In the same way, Serial ATA has the advantages of using a non-row pin design interface and supporting hot-swappable features.
Will parallel ATA still exist after Serial ATA is launched?
Overall, the advantages of serial ATA are obvious. Of course, there are some relatively low-speed devices in the use of parallel ATA, such as optical drive, burner and other devices, parallel ATA transmission rate has been able to meet the needs, so, parallel and serial will coexist for a long time. Of course, Serial ATA supports all ATA devices, as well as devices such as optical drives, but Serial ATA is now used first on the hard drive and will support more storage devices in the future.differences between IDE interface and SATA interfaceThe hard disk interface is a connecting part between the hard disk and the host system, which transmits data between the hard disk cache and the host memory. The different hard disk interface determines the connection speed between the hard disk and the computer, in the whole system, the quality of the hard disk interface directly affects the program running speed and performance. From the home user's point of view, the hard disk interface is divided into IDE, SATA two kinds of specifications, but they have their own advantages and characteristics, users need to choose according to their own circumstances.
IDE interface hard disk is commonly known as the parallel specifications of the PATA hard disk, the majority of desktop storage systems are called Ultra-ata parallel bus interface hard disk products, such specifications are since the 80 has been used in desktop systems as the mainstream of internal storage interconnection technology, Because the use of the field is very extensive time and more than Zhang, so the mature technology brings the large-scale integration of manufacturing low-cost and rapid development of large capacity.
Due to the long time unchanged, in the data transmission, this IDE interface hard disk seems to have some lag, because the current mainstream PATA hard disk can only support ata/100 and ata/133 two kinds of data transmission specifications, the highest transmission rate can reach only 100 or 133MB per second, This can only meet the current general situation of large-capacity hard disk data transfer. In addition, the 80-pin data cables used by this type of hard disk are cluttered inside the chassis, which can hinder the airflow of the air in the chassis, thus affecting the cooling of the system. Although the disadvantage is obvious, but for some old users, because the original motherboard platform does not support SATA interface, this IDE interface pata large-capacity hard disk is preferred, and some users think that this type of hard disk is technically mature, stable, so also choose this type of PATA hard disk.
Composed of Intel, Dell, Seagate, Maxtor, and Apt, serialata.org, introduced new technology specifications for hard disks, serial ATA, serial interface, and Seagate announced the serial ATA 1.0 standard at the IDF Fall 2001 Conference, Officially announced the establishment of SATA specifications This is also the hardware recently promulgated a standard.
In the technical characteristics, we have to admit that Pata hard disk in the installation, transmission speed and power, seismic, noise and other aspects are inferior to SATA hard drives. Because SATA hard disk it has faster external interface transfer speed, better data verification measures, SATA 1.0 specification of the standard transmission rate can reach 150mb/s, so that you can give full play to the Serial ATA interface performance advantages, because the ATA100 theoretical value is 100mb/s, Even ATA133 is the highest 133mb/s. In addition, the SATA connector is very convenient to install first, and SATA is the most important feature is to support hot plug. Serial SATA way through better data verification, signal power down can effectively reduce all kinds of interference, so as to greatly improve the efficiency of data transmission, and the new SATA hard drive cable is also more conducive to the internal chassis cooling.
SATA is not only the advantages, in the shortcomings is also obvious, because the SATA specifications are not very mature, this type of hard disk for FSB requirements than the parallel size of the hard disk, if the user has overclocking the situation must pay attention, because it will often appear to find hard disk or data corruption. Currently support SATA 2.0 of the hard drive has also been introduced, I believe that the SATA 3.0 will also appear in the market, but not the standard the higher the better, for the time being the SATA2.0 specification of the hard disk is mainly for the server and network storage applications, such as ordinary consumers choose SATA 1.0 specifications of the hard disk products sufficient.
General Pata of the hard drive transmission speed are:
Ultra-ata33
Ultra-ata66
ultra-ata100 [
ultra-ata133
SATA hard Drive transfer speeds are:
ultra-ata150the difference between a SCSI interface and a SAS interfaceSAS (serial Attached SCSI), serial attached SCSI, is the next generation of SCSI technology, and is the same as the current serial ATA (SATA) hard drive, using serial technology to achieve higher transmission speed and improve internal space by shortening the link line. SAS is a new interface developed after the parallel SCSI interface. This interface is designed to improve the performance, availability, and extensibility of the storage system and to provide compatibility with SATA hard drives.
SAS interface technology can be backward-compatible with SATA. Specifically, the compatibility of the two is mainly embodied in the physical layer and the protocol layer compatibility. In the physical layer, the SAS interface and SATA interface are fully compatible, SATA hard disk can be directly used in the SAS environment, from the interface standard, SATA is a child standard SAS, so the SAS controller can directly control the SATA hard drive, but SAS is not directly used in the SATA environment, Because the SATA controller does not control the SAS hard drive, at the protocol layer, SAS consists of 3 types of protocols for data transmission based on the different devices connected. Where the serial SCSI Protocol (SSP) is used to transmit SCSI commands, SCSI Management Protocol (SMP) is used for the maintenance and management of connection devices, and the SATA Channel Protocol (STP) is used for data transmission between SAS and SATA. So with these 3 protocols, SAS can be seamlessly integrated with SATA and some SCSI devices.
The back panel (backplane) of the SAS system can connect both a dual-port, high-performance SAS Drive and a high-capacity, Low-cost SATA Drive. So SAS drives and SATA drives can exist in one storage system at the same time. However, it should be noted that the SATA system is not compatible with SAS, so SAS drives cannot be connected to the SATA backplane. Because of the compatibility of SAS system, enabling users to use different interface of hard disk to meet the requirements of various applications in capacity or efficiency, so in the expansion of the storage system with more flexibility, so that storage equipment to maximize investment benefits.
In the system, each SAS port can connect up to 16,256 external devices, and SAS take direct point-to-point serial transmission, the rate of transmission up to 3Gbps, it is estimated that there will be 6Gbps or even 12Gbps of high-speed interface appears. The SAS interface has also been greatly improved, providing a 3.5-inch and 2.5-inch interface that can be tailored to the needs of different server environments. SAS relies on the SAS extender to connect more devices to the current extender with 12 ports, but according to the board manufacturer's product development plan, a 28, 36-Port Extender will be introduced in the future to connect SAS devices, host devices, or other SAS extenders.
Compared with the traditional parallel SCSI interface, SAS is not only significantly improved in interface speed (now the mainstream ultra-320mb/sec SCSI speed is the same, and SAS
Just start speed to reach 300mb/sec, the future will reach 600mb/sec or even more), and because of the use of serial cable, not only can achieve longer connection distance, but also to improve anti-jamming ability, and this thin cable can also significantly improve the internal cooling of the chassis.
The current deficiencies of SAS are mainly as follows:
1 hard disk, control chip types: Only Seagate, the extension and Fujitsu, such as a few hard disk manufacturers launched the SAS interface hard disk, the variety is too small, other manufacturers of SAS hard drive most in the product internal testing phase. In addition, the surrounding SAS controller chip or some of the SAS card type is not much, mostly concentrated in the LSI and Adaptec company hands.
2 Hard drive prices are too expensive: SAS drives are much more expensive than the same volume ultra-hardware SCSI hard drives. The high price has a direct impact on the number of users and the number of channels of digestion, and can not form a mass production of SAS hard drives, the cost of the pressure will in turn lead to price can not be reduced. If users want to make a simple raid level, they need not only buy multiple SAS drives, but also buy expensive raid cards that are basically the same price as the hard drive.
3 The actual transmission speed change is not large: the interface speed of the SAS hard drive does not represent the speed of data transmission, the mechanical structure of the hard disk is limited, now the mechanical structure of SAS hard disk and SCSI hard drive is almost the same. At present, the bottleneck of data transmission is focused on the internal data transmission speed of hard disk, which is determined by the internal mechanism of hard disk and hard disk storage technology, and the speed of disk, which is about 80MBSEC, the performance of SAS hard disk is not improved.
4 User pursuit of mature, stable products: From now launched products, SAS hard disk is more used in high-end 4-way server, and more than 4 server users are not blindly pursuit of high speed hard disk interface technology, the most attractive to them should be mature, stable hardware products, Although the SAS interface server and SCSI interface products in the same speed, stability, but the current technology and products are not mature enough.
However, as Intel and other motherboard chipset manufacturers, Seagate and other hard disk manufacturers and a large number of server manufacturers to promote, SAS related product technology will gradually mature, the price will gradually fall, sooner or later, will become the mainstream server hard disk interface.