How to distinguish hard disk quality

The data interface of the hard disk is mainly IDE (PATA), SATA, SCSI, SAS, optical fiber and so on. Among them, SCSI, SAS and fiber and other interfaces are mainly used for servers and workstations, for desktop-grade products, mainly PATA and SATA-based, Pata is what we often say the 80-pin IDE interface, currently has PATA100 and PATA133 as the mainstream products, but in SATA2 ( SATA 3gb/s) interface HDD has been gradually fading out of the market under large-scale popularization. Therefore, for the mainstream 320GB hard disk, we mainly for the use of SATA2 interface products to test, and for the imminent exit of the market PATA products, unless there are special needs, otherwise we do not have to pay attention.

Here we briefly introduce the SATA interface specification. corresponding to PATA (parallel ATA), SATA data transmission is carried out serially, so it can achieve higher transmission speed than parallel interface, SATA 1.0 can achieve 1.5gb/s transmission speed, and SATA2 can achieve 3gb/s transmission speed. However, it is necessary to suggest that the SATA interface that is not able to reach the 3gb/s transmission speed can be called the SATA2,SATA2 specification in addition to the transmission speed must reach 3gb/s, but also must support NCQ (Native command Queuing, native command queue), Port Multiplier, interleaved start (staggered spin-up) and a series of technologies. Of course, we are accustomed to still call SATA 3gb/s equipment for SATA2 equipment, but we have to understand the details of it.

Currently support SATA 3GB/S interface HDD products can be switched between SATA1.0 and SATA 3gb/s mode, usually by jumper to set, only Hitachi's products are set by software.

The concept of capacity to believe that everyone is very clear, but to put forward is that hard disk manufacturers are generally based on the 1mb=1,000,000bytes formula to calculate the total capacity of the hard disk, so the actual format of the capacity will be less than the hard disk on the label (the system is calculated by 1kb=1024bytes), 320GB is approximately 300GB after formatting with NTFS format.

Single disc capacity is the focus of the current development of hard disk, almost is the standard of hard disk grade. We know that the way to drive capacity is to increase the number of discs, on the other hand, increase the data density of the platters. Simply increase the number of discs is a direct way to increase the capacity of the hard disk, but after all, it will be heat, hard disk volume limits, the current number of discs is up to 5, in the case of the number of discs can not be increased, the increase in single-disc capacity is the only way to increase the capacity of the hard disk.

Increase the single disc capacity in addition to reducing the use of platters, heads to reduce manufacturing costs, due to the increase in recording density, so that the data of the head once read also increased, thereby increasing the internal transmission speed of the hard disk. At present, many hard disk manufacturers have introduced the use of vertical recording technology of hard disk products, relative to the traditional level of recording, vertical recording greatly increased the record density of the hard disk, so the use of vertical recording of the hard disk can achieve a high single-disc capacity, For example, the vertical record of the Seagate cool 7200.10 hard disk, a single disk capacity to reach 188GB, 320GB capacity to achieve only two discs can be, so we now buy hard disk, it is best to choose the vertical recording technology products, performance will be better.

The average seek time is one of the most important performance parameters, which is affected by the speed of the hard disk and the recording density. In the case of 7200rpm rpm, the higher the recording density of the hard disk, the shorter the average seek time--very simple, due to the increase of recording density, the head only need to move a shorter distance to achieve positioning. A shorter average seek time means that the hard drive performs better when reading and writing a large number of small files, because the head is the most frequently moving.

In the current case of 320GB hard drives, due to the use of vertical recording technology, recording density greatly increased, so their nominal average seek time is below 9ms, compared to the previous generation of products significantly faster.

Cache, RPM and motor

Cache as a buffer zone in the hard disk, adjust the data transfer between the two, the size of the cache directly affect the performance of the hard disk, especially a large number of small files read and write. Different hard disk cache size, in terms of current products, 8MB cache is more common, such as 320GB such as large-capacity hard disk is generally equipped with 16MB cache, so when reading and writing a large number of small files, performance will be better.

Speed is the main factor affecting the performance of the hard disk, the current mainstream hard drives are used 7200rpm design, but also some high-end products using 10000rpm design, but high speed brought high calorific value and motor bearing rapid wear is also obvious, which in a certain extent also reduced the reliability of hard disk products, So at present, the 7200rpm is a more balanced performance and reliability of the scheme.

The drive uses the servo motor-that is, we say the motor, it is used by the bearing technology is very important, directly affect the hard disk work noise and durability, and the current mainstream hard disk products have adopted a liquid bearing design, it is to replace the ball with oil film, so as to avoid direct friction metal surface, The heat generated by noise and friction is minimized, the wear of the bearing is reduced, and the life of the hard disk is prolonged.