Hard drive overview: Hard drive (called hard drive in Hong Kong and Taiwan, English name: Hard Disc Drive, HDD for short, full name Winchester hard drive) is one of the main storage media of the computer, consisting of one or more Made of aluminum or glass discs. These discs are covered with ferromagnetic material. The vast majority of hard drives are fixed hard drives, permanently sealed and secured within the hard drive. Several data to judge the quality of the hard drive: 1. Hard drive interface ATA, the full name of Advanced Technology Attachment, uses a traditional 40-pin parallel port data cable to connect the motherboard and the hard drive. The maximum external interface speed is 133MB/s because of the anti-interference of the parallel port cable. The performance is too poor, and the cable takes up space, which is not conducive to computer heat dissipation. It will gradually be replaced by SATA.
IDE
The full English name of IDE is "Integrated Drive Electronics", which is "electronic integrated drive", commonly known as PATA parallel port.
SATA
Hard drives using the SATA (Serial ATA) port are also called serial hard drives and are the future trend of PC hard drives. In 2001, the Serial ATA Committee composed of major manufacturers such as Intel, APT, Dell, IBM, Seagate, and Maxtor officially established the Serial ATA 1.0 specification. In 2002, although Serial ATA related equipment has not yet been officially launched, Serial ATA The ATA committee has taken the lead in establishing the Serial ATA 2.0 specification. Serial ATA uses a serial connection method. The Serial ATA bus uses an embedded clock signal and has stronger error correction capabilities. Compared with the past, its biggest difference is that it can check the transmission instructions (not just data). If Errors are automatically corrected when found, which greatly improves the reliability of data transmission. The serial interface also has the advantages of simple structure and support for hot swapping.
SATA2
Seagate adds NCQ local command array technology to SATA and increases the disk speed.
SCSI stands for Small Computer System Interface. It has gone through many generations of development, from the early SCSI-II to the current Ultra320 SCSI and Fiber-Channel. The connector types There are many kinds. SCSI hard drives are widely used in workstation-level personal computers and servers because they rotate quickly, up to 15,000 rpm, and consume less CPU computing resources during data transmission. However, the unit price is also more expensive than ATA and SATA hard drives of the same capacity.
SAS (Serial Attached SCSI) is a new generation of SCSI technology. Like SATA hard drives, it uses serial technology to obtain higher transmission speeds, which can reach 3Gb/s. In addition, the internal space of the system is improved by reducing the connection cables.
In addition, since SAS hard disks can share the same backplane as SATA hard disks, in the same SAS storage system, SATA hard disks can be used to replace some expensive SCSI hard disks, saving overall storage costs. cost. 2. Hard drive manufacturer EMC
EMC is an American information storage information technology company whose main business is information storage and management products, services and solutions. EMC Corporation was founded in 1979 and is headquartered in Hopkinton, Massachusetts
EMC Clariion CX500 EMC Corporation's stock symbol is EMC, trades on the New York Stock Exchange, and is a component of the S&P 500.
Seagate
Seagate Technology (English: Seagate Technology, NYSE: STX) is one of the world's major hard drive manufacturers. It was established in 1979 in California, USA. Registered in the Isles of Man. Currently, Seagate's main products include desktop hard drives, enterprise hard drives, laptop hard drives and micro hard drives. Among manufacturers that specialize in the development of hard drives, Seagate has the longest history.
Its first hard drive product has a capacity of 5MB. In May 2006, Seagate Technology acquired another hard drive manufacturer, Maxtor Corporation. In terms of product sales, Seagate reported that it was the first company to sell 1 billion hard drive products.
Western Digital (Westdigital)
The market share is second only to Seagate. Mainly desktop products. Its desktop products are divided into the Black series (commonly known as "black disk") which focuses on high IO performance, the ordinary Blue series (commonly known as blue disk), and the environmentally friendly Green series (commonly known as green disk) which focuses on low power consumption and low noise.
Western Digital also provides the Raid Edition series for enterprise nearline storage, referred to as the RE series. There are also 10000RPM Raptor series and VelociRaptor series with SATA interface.
Hitachi
The third largest hard drive manufacturer. Mainly developed from the acquisition of the original IBM hard disk department.
Hitachi Manufacturing Co., Ltd. (Japanese: Hitachi Manufacturing Co., Ltd.; English: Hitachi, Ltd.), referred to as Hitachi, is headquartered in Tokyo, Japan. It is committed to household appliances, computer products, semiconductors, industrial machinery and other products. It is Japan's largest comprehensive motor manufacturer.
Samsung
Samsung Electronics (Samsung Electronics KSE: 005930, KSE: 005935, LSE: SMSN, LSE: SMSD) is the world's largest electronics industry company, Samsung Group One of the subsidiaries. It was established in Daegu Metropolitan City, Republic of Korea in March 1938. The founder was Lee Byung-cheol, and the current president is Lee Kun-hee. It started as an exporter, but soon it branched into many other areas. Today it has more than 200,000 employees in 58 countries around the world. In 2003, its turnover value was US$101.7 billion. Among the list of the 100 most famous trademarks in the world, Samsung Electronics is the only Korean trademark and a symbol of Korean national industry.
Maxtor
Maxtor is an American hard drive manufacturer founded in 1982. In 2006, it was acquired by Seagate, another hard drive manufacturer. [1] Before the acquisition in December 2005, Maxtor was the world's third largest hard drive manufacturer. Maxtor now operates as a subsidiary of Seagate Corporation. Maxtor operates in both the desktop computer and server markets. Compared to speed, Maxtor focuses more on hard drive capacity.
Toshiba
It is Japan's largest semiconductor manufacturer and the second largest integrated motor manufacturer, and is part of the Mitsui Group. Toshiba was formed in 1939 through the merger of two Japanese companies.
Toshiba is an important member of the world's chip manufacturers. In February 2009, Toshiba acquired Fujitsu's hard drive department.
Fujitsu
Fujitsu Co., Ltd. (Fujitsū Kabushiki-gaisha) is a Japanese company specializing in the production of semiconductors, computers (supercomputers, personal computers, servers), communication devices and Services, headquartered in Tokyo.
In February 2009, Toshiba acquired Fujitsu's hard drive department. Generally speaking, the larger the capacity of the hard drive, the cheaper the price per byte, but there are slight exceptions for hard drives that exceed the mainstream capacity. As of early December 2008, the price of a 1TB (1000GB) Seagate hard drive in Zhongguancun was RMB 700, and a 500G hard drive was about RMB 320.
3. Rotation speed
Rotation speed (Rotation Speed ??or Spindle speed) is the rotation speed of the motor spindle in the hard disk, which is the maximum rotation speed that the hard disk platter can complete in one minute. number. The speed of rotation is one of the important parameters that indicates the grade of the hard disk. It is one of the key factors that determines the internal transmission rate of the hard disk and directly affects the speed of the hard disk to a large extent. The faster the hard disk rotates, the faster the hard disk searches for files, and the relative transmission speed of the hard disk is also improved. The hard disk speed is expressed in revolutions per minute, and the unit is RPM. RPM is the abbreviation of Revolutions Per minute, which is revolutions per minute.
The larger the RPM value, the faster the internal transfer rate, the shorter the access time, and the better the overall performance of the hard drive.
The spindle motor of the hard disk drives the platter to rotate at high speed, creating buoyancy that causes the magnetic head to float above the platter. To bring the sector of data to be accessed under the head, the faster the rotation speed, the shorter the waiting time. Therefore, the rotational speed determines the speed of the hard drive to a large extent.
The speeds of ordinary hard drives for home use generally include 5400rpm and 7200rpm. High-speed hard drives are also the first choice for desktop users; while for notebook users, 4200rpm and 5400rpm are the main ones, although some companies have already released 7200rpm notebook hard drives are still relatively rare in the market; server users have the highest requirements for hard drive performance. SCSI hard drives used in servers basically use 10000rpm, and there are even 15000rpm, and their performance is much higher than that of household products. Higher rotational speed can shorten the average seek time and actual read and write time of the hard disk. However, as the hard disk rotation speed continues to increase, it also brings negative effects such as temperature increase, increased motor spindle wear, and increased operating noise. The rotation speed of laptop hard drives is lower than that of desktop hard drives, which is affected to a certain extent by this factor. The internal space of the notebook is small, and the size of the notebook hard drive (2.5 inches) is also designed to be smaller than the desktop hard drive (3.5 inches). The temperature rise caused by the increase in rotation speed puts higher requirements on the heat dissipation performance of the notebook itself; the noise becomes louder. , and necessary noise reduction measures must be taken, which puts more requirements on notebook hard drive manufacturing technology. At the same time, the increase in rotational speed, while keeping other things unchanged, means that the power consumption of the motor will increase, the more electricity will be consumed per unit time, and the working time of the battery will be shortened, which will affect the portability of the notebook. Therefore, laptop hard drives generally use relatively low-speed 4200rpm hard drives.
The rotational speed changes with the improvement of hard disk motors. Now fluid dynamic bearing motors (Fluid dynamic bearing motors) have completely replaced traditional ball bearing motors. Liquid bearing motors are usually used in the precision machinery industry. They use mucous membrane liquid oil bearings, using oil films instead of balls. This can avoid direct friction on the metal surface and minimize noise and temperature; at the same time, the oil film can effectively absorb vibration, improving the earthquake resistance; it can also reduce wear and extend service life.
4. Average Access Time
Average Access Time refers to the time when the magnetic head reaches the target track position from the starting position and finds the data to be read and written from the target track. The time required for the sector.
The average access time reflects the read and write speed of the hard disk, which includes the seek time and waiting time of the hard disk, that is: average access time = average seek time + average waiting time.
The average seek time of a hard disk (Average Seek Time) refers to the time required for the hard disk's magnetic head to move to a specified track on the disk surface. Of course, the smaller the time, the better. Currently, the average seek time of hard disks is usually between 8ms and 12ms, while SCSI hard disks should be less than or equal to 8ms.
The waiting time of the hard disk, also called latency, refers to the time it takes for the magnetic head to be on the track to be accessed and waiting for the sector to be accessed to rotate under the magnetic head. The average waiting time is half of the time it takes for the disc to rotate once, and should generally be less than 4ms.
5. Transfer rate
Transfer rate (Data Transfer Rate) The data transfer rate of the hard disk refers to the speed at which the hard disk reads and writes data. The unit is megabytes per second (MB/s). ). The hard disk data transfer rate also includes internal data transfer rate and external data transfer rate.
Internal Transfer Rate (Internal Transfer Rate) is also called Sustained Transfer Rate (Sustained Transfer Rate), which reflects the performance of the hard disk buffer when it is not used. The internal transfer rate mainly depends on the rotation speed of the hard disk.
External Transfer Rate (External Transfer Rate) is also called Burst Data Transfer Rate (Burst Data Transfer Rate) or interface transfer rate. It is nominally the data transfer between the system bus and the hard disk buffer. The external data transfer rate is related to the hard disk interface type and the size of the hard disk cache.
At present, the maximum external transfer rate of Fast ATA interface hard disk is 16.6MB/s, while the Ultra ATA interface hard disk reaches 33.3MB/s.
Hard drives using the SATA (Serial ATA) port are also called serial hard drives and are the future trend of PC hard drives. In 2001, the Serial ATA Committee, composed of major manufacturers including Intel, APT, Dell, IBM, Seagate, and Maxtor, formally established the Serial ATA 1.0 specification. In 2002, although Serial ATA related equipment has not yet been officially launched, the Serial ATA Committee has taken the lead in establishing the Serial ATA 2.0 specification. Serial ATA uses a serial connection method. The Serial ATA bus uses an embedded clock signal and has stronger error correction capabilities. Compared with the past, its biggest difference is that it can check the transmission instructions (not just data). If Errors are automatically corrected when found, which greatly improves the reliability of data transmission. The serial interface also has the advantages of simple structure and support for hot plugging.
Serial hard disk is a new type of hard disk interface that is completely different from parallel ATA. It is famous for its use of serial method to transmit data. Compared with parallel ATA, it has many advantages. First of all, Serial ATA transmits data in a continuous serial manner, and only 1 bit of data is transmitted at a time. This can reduce the number of pins in the SATA interface, reduce the number of connecting cables, and be more efficient. In fact, Serial ATA can complete all the work with only four pins, which are used to connect cables, connect ground wires, send data, and receive data. At the same time, this architecture can also reduce system energy consumption and reduce system complexity. Secondly, Serial ATA has a higher starting point and greater development potential. The data transfer rate defined by Serial ATA 1.0 can reach 150MB/s, which is higher than the highest data rate of 133MB/s that the fastest parallel ATA (i.e. ATA/133) can achieve. The transfer rate is still high, and the data transfer rate in Serial ATA 2.0 reaches 300MB/s. Eventually, SATA will achieve a maximum data transfer rate of 600MB/s.
6. Cache
Same as the cache on the motherboard (RAM Cache), the purpose of the hard disk cache is to solve the problem of mismatch in read and write speeds between the front and rear stages of the system, so as to improve the performance of the hard disk. reading and writing speed. Currently, most SATA hard drives have an 8M cache, while Seagate's "Barracuda" series uses a 32M Cache.