Basic knowledge of hard disk

Currently on the market the hard drive in addition to the Bigfoot (Bigfoot) series is 5.25-inch structure, the others are 3.25-inch products, of which 5.25 inches also have a semi-high and full height of the points. Using the external structure of the 5.25-designed BigfootTX4.0 hard drive, the 3.25-inch hard drive structure is similar to this.

1, interface

Including the power socket and data interface two parts, wherein the power socket and the host power supply, for hard disk work to provide power assurance. The data interface is the link between the hard disk data and the motherboard controller, which is divided into Eide interface and SCSI interface according to the difference of the connection mode. The Eide interface is used for most hard drives because of its low cost and convenient use. The SCSI interface must be equipped with a SCSI card to use, although the price is relatively high, but it has excellent transmission performance, more in the computer network servers and high-end graphics workstations and other equipment used.

2. Control circuit board

The use of SMD components welding, including spindle speed control circuit, head drive and servo positioning circuit, reading and writing circuits, controls and interface circuits. On the circuit board there is also an efficient single-chip ROM chip, its curing software can be the initialization of the hard disk, the implementation of power and start spindle motor, electric initial seek, positioning and fault detection. The control circuit board is exposed to the hard disk surface on the basis of stable operation and enhanced heat dissipation. There is also a cache chip installed on the circuit board, usually 128KB or 256KB, and the latest product has been gradually using 215KB data caching in order to achieve higher transmission efficiency.

3. Fixed cover plate

In fact, it is the hard disk of the panel, to mark the product model, origin, set data, and the bottom of the combination of a sealed whole, to ensure the hard disk disc and the stable operation of the mechanism.

4, Installation screw hole

For the installation of the hard disk, for 3.25-inch products, fixed cover plate and side have mounting holes, can be easily and flexibly placed.

Internal structure of hard disk

The internal structure of the hard disk consists of a fixed panel, a control circuit board, a pan head component, an interface, and an attachment, and the head component (Hard disk Assembly,hda) is the core of the hard disk and is encapsulated in the purifying cavity of the hard disk, including the floating heads, the drive mechanism, the disc Front read and write control circuit.

1. Floating head ASSEMBLY

It is composed of read-write head, transmission arm and drive shaft. The magnetic head is the most important and key part of hard disk technology, in fact, it is a combination of several heads made of integrated process, it adopts non-contact head and disk structure, and then flies on the high speed rotating disk surface after electric power, so the high data transmission rate can be obtained by 0.1-0.3μm. Now the speed of up to 5400rpm hard drive fly high are lower than 0.3μm, in order to facilitate the reading of higher signal-to-noise ratio signal, provide data storage reliability. Because of the limitation of the magnetic induction head used in the early hard disk, the new type of magnetoresistive heads magnetic resistance Head is adopted in the novel large capacity hard disk products.

The Mr Magnetic-resistance head is made up of a read-write separation head structure, which uses the traditional magnetic-induction head while the writing is used, and the Mr Head is used for the read operation. The separation design can be optimized for the different characteristics of the head to obtain the best read and write performance.

Because the Mr Magnetic head is made of special material, the resistance value and current of Mr Element can be changed under the magnetic field, and when the disc is flying over the head surface, the signal is sensitive to the signal change, and the accuracy of the data reading is very high. At the same time, Mr Magnetic head has a very narrow density, the disk track can be done very much the corresponding overall density will increase, so that the disc capacity can be achieved in GB. With the development of technology, the GMR (Giant magnetoresistive heads) head, which is made of multilayer structure and better magnetic resistance effect, is also used in the oversized hard disk with a narrower channel density.

2. Head Drive mechanism

It is composed of a voice coil motor and a head drive car, and a new type of large-capacity hard disk has an efficient anti-vibration mechanism. The high precision light Head drive mechanism can correctly drive and position the head, and accurately locate the track specified in the system instruction in a short time to ensure the reliability of data reading and writing. The motor of the head mechanism has three kinds of stepper motor, moment motor and voice coil motor, the first two kinds of applications in the low capacity hard disk, has been eliminated, the large capacity hard drive uses the voice coil motor drive more.

The voice coil is inserted in the middle with the magnetic head connected with the magnet of the coil, when the current through the coil, the magnet will occur displacement, and then drive the load head of the car, and according to the controller in the disk head position information coding to get the head moving distance, to achieve accurate positioning. Voice coil motor is a sealed control system, can automatically adjust, faster than the early driving motor and high safety factor.

3, platters and spindle components

Disc is the hard disk storage data carrier, now most of the platters using metal film disk, this metal film than the floppy disk of the discontinuous particle carrier has a higher record density, but also has high residual magnetism and high coercivity characteristics.
The spindle assembly includes spindle components such as bearing pads and drive motors. With the expansion of the hard disk capacity, the speed of the spindle motor is also increasing, the speed of the spindle motor is also increasing, which leads to the disadvantage of the traditional ball bearing motor wearing, rising temperature and increasing noise, which has a negative effect on the speed improvement. As a result, manufacturers began to use the precision machinery industry liquid shaft motor (FLUID dynamic bearing motors) technology, liquid bearing motor using mucosal liquid oil bearings, oil film instead of the ball can avoid the metal surface of the direct friction, noise and temperature reduced to the lowest. And oil film has the ability to absorb vibration effectively, can improve the seismic capacity of spindle parts, in theory, liquid bearing motor without wear, life is infinitely long, is the development trend of ultra-high speed hard disk.

4. Front control circuit

The front amplification circuit controls the signal of the magnetic head, the spindle motor speed, the head drive and the servo positioning, because the signal of the magnetic head is weak, the amplification circuit can be sealed in the cavity to reduce the interference of the external signal and improve the accuracy of the operation instruction.

5. Other new technologies

PRML (Partial Response Maximum likelyhood, the most similar local response) Read channel technology. The application of PRML technology in hard disk signal reading can avoid the signal interference caused by the narrow track, and greatly improve the density of the disc. At the same time, due to the increase of disk density, the magnetic head can read more signals in the same period, which makes the reading speed improve. Multi-point sampling through the maximum similarity principle can compare the signal read by the magnetic head to the standard signal to get the most matching signal and transmit it, thus greatly improving the accuracy of the data reading. The common use of PRML technology makes the capacity, speed and reliability of the hard disk improve with different degrees.

s.m.a.r.t. Technology. s.m.a.r.t. (Self-monitor-ing,analysis and Reporting Technology) is self-monitoring, analysis and reporting technology, which can monitor the head, disk, motor, circuit, etc. The monitoring circuit of the hard disk and the monitoring software on the host are analyzed and compared with the historical record and the preset security value, and the warning is automatically issued to the user when the security value is out of range. And more advanced technology can automatically reduce the speed of the hard disk, the important data files to other security sector, through the s.m.a.r.t. Technology can predict the potential failure of the hard disk effectively and improve the security of the data.

How the hard drive works

After the hard drive power is working properly, the initialization of a stand-alone module in the control circuit is performed, at which point the head is placed at the center of the disc, the spindle motor is started and the main shaft is set to rotate at high speed, the car body with the head is moved, the floating head is placed on the 00-way of the platter surface, and the When the interface circuit receives the instruction signal from the microcomputer system, through the preamplifier control circuit, driving the voice coil motor to send out the magnetic signal, according to the change of the induction resistance of the magnetic head to the disc data information correctly positioned, and the received data information decoding, through the amplification control circuit transmission to the interface circuit, feedback to the host system to complete the instruction operation. At the end of the hard drive operation, the floating head resides in the center of the disc under the action of the inverse moment spring.

Three types of control modes for hard drives

LBA Mode: Logical block setting, the maximum manageable hard disk capacity of 8.4GB, the best way to set up a large-capacity hard disk.

Large mode: Mode setting, the maximum manageable hard disk capacity is 1GB, and does not support the LBA mode of the hard disk controller can choose to use.

Normal mode: Normal settings, the original hard drive management mode, can manage hard disk capacity of only 504M. Large-capacity hard drives, if set in this way, can only manage to 504M.

Maintenance of hard disk

High-speed reading of hard disk and effective data storage performance is unmatched by any other carrier, relatively speaking, due to advanced technology and precision, the failure rate of hard disk is usually lower than other storage devices. However, only proper maintenance and use can ensure the best performance of the hard drive.

1, to ensure the normal working environment, vibration, humidity, voltage instability can lead to hard disk damage.

2, do not easily the low-level format of the hard disk operation, to avoid the disc performance of unnecessary impact.

3, to avoid frequent advanced format operation, it also affects the performance of the disk, without repartition, you can use the parameter "Q" of the Quick format of the command.

4, the hard drive in the case of bad, even a cluster may have a proliferation of destructive, in the warranty period should be found as soon as possible to find merchants and manufacturers to replace or repair, has been the warranty period as far as possible to reduce the format of the hard disk, reduce the spread of bad clusters.
5, because the hard disk is in the dust-free Super Purification workshop assembly, remember not to open the hard drive of the cover plate, high-speed low flying head assembly rotation-driven dust or dirt can cause the head or disc damage, resulting in data loss, even if still can continue to use, hard disk life will be greatly shortened.