At present, most hard disks are Winchester disks in structure. Since IBM produced the first Winchester hard disk in 1973, all hard disks have basically adopted this structure, which is Winchester technology. Its core is that the disk is sealed, fixed and constantly rotating at high speed, and the magnetic head is suspended above the disk and moves along the radial direction of the disk without contacting the disk.
2. Magnetic head technology
The hard disk reads data through the head. The earliest traditional magnetic head is electromagnetic induction magnetic head, which is integrated with reading and writing. Because of the different reading and writing operations of hard disk, this two-in-one magnetic head must take into account both reading and writing characteristics, which brings inconvenience to the design of hard disk. Later, the hard disk began to adopt MR (magnetoresistive head technology) head, which is a separate head structure: the writing head still uses magnetic induction head, while the MR head is used as read head magnetoresistance. In this way, better read/write performance can be obtained. MR magnetic head senses the signal amplitude through the change of resistance, which is quite sensitive to the signal change and has high accuracy. Moreover, since the amplitude of the read signal has nothing to do with the track width, the track can be made very narrow, thus increasing the disk density and expanding the disk capacity. However, with the increase of storage capacity per disk, the reading limit of MR head finally reached, so GMR (Giant Magnetoresistive Head Technology) head was born. Now, GMR heads are used in more than 5G models of storage per disk. After entering 200 1, almost all hard disks adopt GMR. GMR magnetic head technology is developed on the basis of MR, which has higher sensitivity than Mr. It is based on more and more advanced magnetic head technology that it is possible to make the storage capacity of hard disk more and more. At present, the latest magnetic head is based on the third generation giant magnetoresistive magnetic head technology.
Step 3 connect
The interface mode of hard disk can be said to be another very important technical index of hard disk, which can be reflected from the huge price difference between SCSI hard disk and IDE hard disk. The interface mode directly determines the performance of hard disk. At present, the most common interfaces are IDE(ATA) and SCSI, and some mobile hard disks use PCMCIA or USB interfaces.
(1)IDE (integrated drive electronics):
IDE interface was originally developed by CDC, Compaq and Western Digital, and the standard was formulated by American National Standards Institute (ATA), so it is also called ATA interface. Almost all the hard disks in our ordinary users' homes are IDE interfaces. Hard disks of IDE interface can be subdivided into ATA- 1(IDE), ATA-2(EIDE), ATA-3 (Fast ATA-2), ATA-4 (including UltraATA, Ultra ATA/33, Ultra ATA/66) and serial ATA (including Ultra ATA/ 100). The data transmission rate of the basic IDE interface is 4.1MB/s. There are two transmission modes, PIO and DMA, and the supported buses are ISA and e ISA. Later, in order to improve the data transmission rate, increase the number of devices that can be connected on the interface, break through the limit of 528M and connect optical drives, ATA-2, ATAPI, FAST-ATA and FAST-ATA2 standards of PCI bus were developed one after another, and the data transmission rate reached 16.67MB/ sec. 1996 quantum and Intel jointly developed the Ultra DMA/33 interface. Strictly speaking, this interface is no longer an IDE interface, but should be called an EIDE interface. PIO mode 5 is adopted, and the data transmission rate reaches 33 MB/s. In 1999, quantum also introduces Ultra DMA/66 interface, which is twice as fast as Ultra DMA/33. CRC (Cyclic Redundancy Cyclic Check) technology is adopted to ensure the security of data transmission, and 80-wire special connection cables are used. At present, the mainstream hard disk interface type on the market is Ultra ATA/66. However, after entering the new century, the most promising hard disk interface type should be Ultra ATA/ 100, and its theoretical maximum external data transmission rate can be as high as100MB/s/s.
(2)SCSI (Small Computer System Interface):
SCSI is not specially designed for hard disks, but is actually a bus interface. Because it works independently of the system bus, its biggest advantage lies in the extremely low system occupancy, but because of its high price, the hard disk of this interface is mostly used in high-end applications such as servers.
4. Capacity
Capacity can be said to be a technical index that users know best about hard disks, and its unit is megabytes (MB) or gigabytes (GB). The two factors that affect capacity are the amount of storage per disk and the number of disks. As the name implies, the storage capacity of each disk is the information capacity that can be stored on a single disk. The larger the capacity of a single disk, the easier it is to realize a large-capacity hard disk, and the time required to find data is relatively reduced. Nowadays, the single disk storage capacity of hard disk is increasing, which can generally reach 20G. The storage capacity of each disk is also increased in the same way.
At the same time, the production cost of hard disk will also be reduced, which is why hard disk manufacturers are competing to launch high-unit disk storage hard disk products first. You may sometimes find that the nominal capacity of the manufacturer is inconsistent with the capacity detected by the computer when you detect the hard disk. This is because they use different conversion units. Manufacturers mostly use 1000 decimal conversion, that is, 1000 bytes, 1000 GB = 1000 MB, while computers mostly use 65438.
5. Hidden objects
Because there is a huge speed difference between CPU operation and hard disk reading, in order to solve the waiting problem of CPU when reading and writing data on hard disk, an appropriate cache is set on hard disk to solve the problem of speed mismatch between the two. The function of hard disk cache is the same as that of the high-speed cache on the motherboard, in order to improve the reading and writing speed of the hard disk. Of course, the bigger the cache, the better. At present, the cache of IDE hard disk is generally between 5 12K and 2M, and the data cache of mainstream hard disk should be 2MB, and the highest data cache of SCSI hard disk has now reached 16MB.
6. Speed
Rotational speed refers to the rotational speed of the motor spindle in the hard disk, and the unit is RPM (revolutions per minute), which directly affects the data transmission rate of the hard disk. Theoretically, the faster the rotating speed, the greater the data transmission rate. At present, the spindle speed of IDE interface hard disk is generally 5400 and 7200rpm (rpm/s), while that of mainstream hard disk is 7200rpm. As for SCSI hard disk, the spindle speed can generally reach 7200 to 10000 rpm, while the highest speed SCSI hard disk can reach 15000 rpm. Faster rotation speed can shorten the time of disk rotation, shorten the average waiting time and average seek time, and find the needed data faster. At the same time, the transmission rate inside the hard disk will also increase, thus speeding up the reading and writing speed.
7. average seek time
The index refers to the time from the time when the head gets the instruction to the time when it finds the track where the data is located. It represents the ability of the hard disk to read data in milliseconds. It should be noted that it is different from the average access time. The shorter the average seek time, the better. Now choose a hard disk, and choose a product below 9 milliseconds.
8. Internal data transmission rate
The internal data transmission rate is the data transmission speed between the hard disk head and the cache, which can be said to be the key to affect the overall performance of the hard disk, and generally depends on the disk speed and data line density of the hard disk. Mb/S or Mbps is often used in this indicator, which means megabits per second. If it needs to be converted to MB/S (megabytes per second), the Mbps data must be divided by 8. For example, some hard disks give the maximum internal data transfer rate of 13 1Mbps, but if calculated in MB/S, it is only16.37 MB/s. At present, the maximum internal data transfer rate of mainstream hard disks on the market is 30MB/s to 45MB/s, which is much lower than UltraATA/1s. It can be seen that the bottleneck of hard disk as a computer at present lies in the data transmission rate inside the hard disk.
9. External data transmission rate
This is the rate at which data is read from the hard disk buffer. It is directly linked to the interface type of the hard disk, so the data interface rate is often replaced by MB/s in advertisements or hard disk characteristic tables. At present, the mainstream hard disks generally adopt Ultra ATA/66, and its maximum external data rate is 66.7 MB/s. The latest Ultra ATA/ 100 interface is adopted. The maximum external data transmission rate can reach 100MB/s/s ... For SCSI hard disk, if the latest Ultra 160/m SCSI interface standard is adopted, its data transmission rate can reach 160MB/s, and the maximum external data transmission of Fibra channel will reach 200MB/s!
10, MTBF (continuous time between failures)
Refers to the longest time from the start of hard disk operation to failure, in hours. Generally, the MTBF of a hard disk is at least 30,000 or 40,000 hours. This index is not provided in general product advertisements or common technical feature tables. If necessary, you can go online to the website of the company specializing in the production of this hard disk.
In addition to these technical indicators mentioned above, there are other factors that affect the performance of the hard disk, such as the time between tracks and the surface temperature of the hard disk, so I won't go into details here. To tell the truth, speaking so much professional content in one breath may not only be difficult for you to digest, but also make my head grow up. But the reason why you insist on the common sense of these terms is that you can have a preliminary understanding of the hard disk, rather than being ignorant.
The second key technical article
As we can see, due to the development of technology, the speed and performance of hard disk have been greatly improved in recent years, but the fundamental reason is that the technological breakthrough of hard disk can only be the following aspects:
Adopt more advanced technology, so that the storage capacity of each hard disk is higher, so as to store more data (this technology is online.
The disk and head efforts mentioned above);
★ Improve the spindle motor of the hard disk to make it rotate at a higher speed, thus reducing the average seek time of the hard disk;
★ Using more advanced hard disk accessory technology, the working stability, data integrity and security of hard disk will be promoted to a new height. It is such an idea that today's hard disks adopt a series of new technologies and will continue to be widely used in the new century:
1, RAID (Thin Array of Cheap Disks) Disk Array Technology
RAID can actually be understood as a method of using disk drives, which connects a group of disk drives in a logical way and uses them as a logical disk drive. The advantages of this technology are low cost, low power consumption, high transmission rate, fault tolerance and higher security, and the price is much lower than that of traditional large-diameter disk drives under the same capacity. RAID is now mainly used for server hard disks, but just like any high-end technology, RAID is also being transferred to PC. Perhaps the day when all PCs use SCSI disk drive RAID is the real "future day" of PCs.
2.PRML (partial response maximum possible mask) reading channel technology.
Simply put, PRML technology divides the hard disk data reading circuit into two "operation pipelines". In the first part of the pipeline, the signals read by the magnetic head are digitized, and then only some "standard" signals are selected and handed over to the second part for further processing. In the second stage, the received signal is compared with the signal model preset by PRML chip, and then the signal with the smallest difference is selected for combined output to complete the data reading process. PRML technology can reduce the error rate of hard disk reading data, so it can further improve the data density of the disk. With the widespread adoption of PRML technology, the capacity, speed and reliability of hard disk have been improved to varying degrees.
3. Self-monitoring, analysis and reporting techniques.
Due to the increasing capacity of hard disk, in order to ensure the security of data, hard disk manufacturers are trying to find hard disk security monitoring mechanism, and S.M.A.R.T technology came into being. S.M.A.R.T is "self-monitoring, analysis and reporting technology". It can monitor magnetic heads, disks, motors, circuits and other components. The monitoring circuit of the hard disk and the monitoring software on the host analyze and compare the operation of the monitored object with the historical record and the preset safety value, and will automatically warn the user once it exceeds the safety value range. Moreover, more advanced technology can automatically reduce the speed of hard disk and transfer important data files to other secure sectors. S.M.A.R.T technology can effectively predict the potential failure of hard disk and improve the security of data.
4.ATA/100 technology
For IDE market, the end of the century can be said to be the world of Ultra ATA/66, which supports the maximum external data transmission rate of 66.7 MB/s hard disk ... In 2000, Quantum Company and Intel and other chipset giants launched ATA/ 100 standard. Theoretically, the maximum external data transmission rate of hard disk it supports is 100MB/s/s, and ATA/ 100 has become the protagonist of new hard disk technology with the efforts of processor manufacturers, chipset manufacturers, motherboard manufacturers and hard disk manufacturers. However, the internal transmission rate of hard disk is the bottleneck that affects the performance of hard disk. Although the internal transmission rate of hard disk is increasing, it can only reach 45MB/S at present, which affects the overall speed of hard disk.
It should be pointed out that although ATA/ 100 needs the support of the corresponding motherboard and uses an independent 80-core interface cable, it can be fully backward compatible and can be used in different modes such as ATA/33 and ATA/66. Moreover, the interface also contains CRC (Cyclic Redundancy Check) feature, which can increase the integrity and reliability of transmitted data and detect errors in data transmission.
5, data protection and vibration protection technology
Hard disk is afraid of vibration. No matter whether the power is turned on or not, as long as the hard disk is hit or vibrated, there will always be some data damaged to some extent. If the hard disk is running, the damage will be even greater. In this respect, DPS (data protection system) and SPS (earthquake prevention system) technologies of former Quantum Company (merged by Maituo Company) and data guarantee technologies of Western Digital Company.
Technology, IBM's DFT(Disk Fitness Test), Maituo's MaxSafe and ShockBlock, Seagate's SeaShield technology, enable the hard disk to withstand the impact of high G number, minimize the damage caused by the impact, provide a good guarantee for the data in the hard disk, and greatly improve the integrity and reliability of the data.
6, the manufacturer's unique technology
In order to improve the market competitiveness of products, many manufacturers have added unique technologies to the hard disk to improve the quality:
(1) Data Lifeguard Technology of Western Digital Company
There is a "data lifeguard" technology in the hard disk of Western Digital, which actually uses S.M.A.R.T technology. Simply put, the hard disk lifeguard will automatically scan and detect the inside of the hard disk eight hours after it is turned on. If it encounters a part that may produce a bad sector soon, it will quickly transfer the data on some sectors to a good sector and make necessary connections to the data on the hard disk. The uniqueness lies in that all the work of the data lifeguard can be started and executed by the hard disk itself, without the cooperation of the motherboard or other tools and programs, so users do not need to install additional tools and software. As long as the power of the hard disk is on, the Data lifeguard will scan, analyze and repair it every eight hours. Moreover, the data lifeguard only works when the hard disk is idle (hard disk 15 seconds is inactive). Once the data lifeguard is ready to start scanning, analyzing and repairing, if there is other work to be done on the hard disk, the data lifeguard will extend 15 minutes before starting work, so don't worry that this function will affect the working efficiency of the hard disk.
(2) DPS technology of former Quantum Company.
DPS(Data Protection Sydtem) is another new technology proposed by former Quantum Company, which allows users to determine whether their hard disk is really faulty. If you feel that the hard disk has some strange performances, such as abnormal noise and sudden slow speed, you can start it with a floppy disk and run the DPS program, which can help you test whether there is any problem with the hard disk. At this time, it will check the basic random tests such as the S.M.A.R.T data buffer of the hard disk, and the most important thing is that all the tests will never affect the data stored in the hard disk. With this tool, we can determine whether the hard disk really needs to be repaired.
(3) MaxSafe and ShockBlock technologies of Maituo Company.
MaxSafe is one of the unique technologies of Maituo Company, which provides the function of ECC. The so-called ECC refers to a complex coding algorithm. When transmitting data, some extra bits are used as authentication codes for error correction. Once there is an error in data transmission, error-correcting codes can be used to repair the incorrect data and ensure the correctness of the data. In the past, the SDRAM memory of PC- 100 and the CPU with Pentium above 350 MHz all had ECC function, and now the hard disk also has this function!
ShockBlock is another new technology adopted by Maituo's new hard disk, which strengthens the rigidity of the steel plate connecting the read-write head, and the read-write head is 40% lighter than the original read-write head. The purpose of these two new designs is to minimize the possibility of the pickup head bouncing off the disk. If the read-write head does not bounce off the disk, there will be no debris when the disk is hit by the read-write head, thus prolonging the service life of the hard disk.