Hard disk (English: H ARD D ISK D Rive, abbreviation: an HDD ) is used on the computer hard disk rotation based on a nonvolatile memory, learn a computer memory
In the flat surface of the magnetic storage and retrieval of digital data, data from a magnetic surface is changed into the head by an electromagnetic flow polarities written to disk,
Data may be read by the disk: magnetic head passes over the disk, the disk itself is a magnetic field results in an electric signal a change in the reading coil
Semi-hard random access manner can read the data in the hard disk in any order, however read the different data rate is different in different locations
The principle:
When the main motor drives the rotation of the disc, a group of sub-motor drive ( heads ) corresponding to the disc, and determines whether the read heads or tails of the disc surface, a head suspension shown in a circular disc concentric with the disc surface track ( track or said cylindrical ), time specified by the head and the magnetic disk using the hard disk manufacturer sensing surface of the magnetic induction coil is positioned to read the time or interval data sectors , whereby the contents of the data sector;
A hard disk including: a disk (one or more high speed rotation) and a sealing head into the hard disk drive,
Has filtered through the pores measures air pressure inside and outside the hard disk used to balance the heat generated during the work resulting from the difference.
Usually by the physical structure of the hard disc and the magnetic head, the motor, the main chip and cable and other components;
Track: When the disk rotates, the head when held in a position, the head will each draw a circular path on the disk surface, the circular path is called a track (Track).
Cylinder: a disk in the group consisting of a plurality of the disc, the disc surface is different, but in a cylindrical surface (Cylinder) a plurality of tracks composed of the same radius of the circle.
Sector: each track on the disk is divided into a plurality of arcs, the arc is hard sector (Sector). The first sector of the hard drive, called a boot sector
MBR and GPT (globally unique master boot record and partition represented)
In order to avoid failure to extend the service life of hard disk
Recommendation: in 30-1 seconds after turning off the hard disk, the hard disk does not move (and laptops)
Because when the power is turned off and have greater shock head immediately to a safe area, but the hard drive at power will reduce the degree of ruggedness (reverse rotation mobility), only moderate movement
The major hard drive manufacturers
how to install:
Press hard disk is divided into different data interface: ATA (also known as IDE), SATA, SCSI and SAS
The current normal hard disk actual data transfer speed is generally not more than 300MB / s.
ATA: full name of Advanced Technology Attachment, is connected to a conventional 40-pin parallel port data lines of the motherboard and the hard drive, interface speed up to 133MB / S , because the poor immunity of parallel lines, and the cable space is larger, the adverse computer internal heat, has gradually been replaced by SATA.
SATA: full name Serial ATA, that is, using serial ATA interface, is characterized by strong anti-interference, the requirements of the data line is much lower than the ATA, and supports hot-plug features. SATA-II interface speed 300MiB / S , and the new standard SATA-III can reach speeds 600MiB / s of. SATA data line much finer than the ATA, facilitates air circulation in the cabinet, the wire is also more convenient sorting.
SCSI: full name of Small Computer System Interface (small computer systems interface), through multiple generations of development, from the early SCSI-II, to the current Ultra320 SCSI and Fiber-Channel (Fiber Channel) interface type is also varied. SCSI hard disk workstation class widely used in personal computers and servers, and therefore the use of more advanced technologies, such as high speed disc rotation speed of 15000rpm, and the data transmission when the CPU occupancy rate is low, but the same capacity than monovalent ATA and SATA hard disk is more expensive.
SAS: full name of Serial Attached SCSI, SCSI is the next generation technology, compatible with SATA hard drives, are taken sequential techniques to obtain higher transmission speeds, up to12Gb / S. In addition also improved the internal space through narrow cable system or the like. Further, since the hard disk drive can share the same SAS backplane with SATA, SAS and therefore in the same storage system may be used to replace some of the expensive SATA drives SAS drives, the overall storage cost savings. SATA storage system but not the SAS hard disk.
FC: Full Fiber Channel (Fiber Channel interfaces), with this hard disk interface in use of hot-pluggable fiber optic coupler, high bandwidth ( 4Gb / S or 10Gb / S) , remote connection characteristics; internal transfer rate than the average higher hard disk. But its high price, so FC interface is typically used only for high-end servers.