How to buy hard disk

Hard disk is one of the important parts of the computer, not only expensive, stored information is priceless, therefore, each purchase of computer users want to choose a cost-effective, stable performance of a good hard drive, and in a period of time to meet their own storage needs. Speed, capacity and security are the three major factors that weigh hard drives. Bigger, faster, safer, cheaper is always the direction of hard disk development. The purchase of hard disk should first be considered from the following aspects:

(i), hard disk capacity

The capacity of the hard disk is very critical, most of the eliminated hard drive because of insufficient capacity, can not adapt to the growing volume of data storage, if the speed is slow to wait, if the lack of space but more headaches. Hard disk capacity is not too much, in the capital of sufficient conditions, should try to buy large-capacity hard disk, this is because the larger the capacity, hard disk on the cost of storage media per megabyte.

In principle, as far as possible, the larger the size of the hard disk, the better, on the one hand, users get more storage space, can better face the potential storage needs in the future, on the other hand, the larger the capacity of the hard disk on the cost per megabyte of storage media, virtually reduce the cost of users, This is especially important for users who are engaged in graphic image processing, audio speech recognition, and multimedia technology applications, which require a huge amount of storage space. But not for all users, for example, for Office applications in general Office PCs with a large size of the hard drive is somewhat "extravagant", and ordinary home users, due to the capital constraints, it is not possible to purchase a large volume of hard drives, but at least at the moment should also buy more than 80GB of hard drives.

The main driving force driving the rapid development of HDD capacity at present is the following two points:

First, with the increasingly development of network applications, the telecommunications network around the increasing capacity, upgrade, network users can enjoy more and more bandwidth, the Internet faster and faster. A consequent problem is that the amount of data downloaded from the Internet will also increase dramatically. This number is used by traditional telephone lines and the ordinary modem do not dare to imagine. For example, cable modem and satellite link technology can provide 30 to 40 megabits per second of data transfer speed. Surfing the internet for a few 10 minutes and pulling back hundreds of trillion files is a piece of cake. Some observers claim that the Internet has a "multiplier effect". According to their forecasts, for everything that is stored online (data), as users around the world continue to download software, pictures, information, video and games, the same things will be repeated thousands of downloads, and eventually lie on the user's hard drive. Although they think this effect will produce some "waste". But the fact is that as home users enjoy more bandwidth, the download of large files becomes easier, and the corresponding demand for hard disk capacity is more and more urgent.

Second, the rapid growth of digital media content, some "storage-intensive" multimedia applications are also stimulating the development of large-capacity drives. These applications include digital TV, photos, movies, music, and so on, and they all have a harsh demand for the storage capabilities of the system. Analysts predict that these applications will become more popular and will be an important factor in sustaining the drive's expansion. Here's a look at how much hard disk space is needed to meet the demands of these exciting digital applications:

• TV: 13GB per hour (with MiniDV format)

• Music: 50MB per series (using MP3 format)

• Movie: 4GB per unit

(b), hard drive speed

Because the hard disk reading and writing can not be separated from mechanical movement, its speed relative to the CPU, memory, graphics and so on the speed is much slower, from the famous "barrel effect" to see that the performance of the hard drive determines the final performance of the computer.

The speed of the hard drive depends mainly on the speed, cache, mean seek time and interface type, in the internal transmission rate (Head → cache rate) has become a bottleneck, just improve the external data transfer rate (improve the interface type) on the overall performance of the impact is not, so we can simply think that the speed of the hard drive is only determined by its speed, Cache size and average seek time.

1. Spindle speed

Speed is one of the most important factors affecting the performance of the hard disk, the current market is 5400rpm (revolutions per minute) and 7200rpm hard drive. Should not choose products less than 5400 rpm, 7200 rpm if the quality of stability should be preferred.

2. Average Seek time

Mean seek time refers to the time that the head is from the command to the track where the data is located, and it describes the ability of the hard disk to read the data in milliseconds. As a prerequisite for the completion of a transmission, the head first needs to quickly find the sector where the data resides, which is called "Mean seek Time" (Averageseektimes). This time the smaller the better, generally choose the average seek time in 10ms below the product.

3. Internal data transfer rate

That is, the data transmission speed between the head to the hard disk cache, which can be said to affect the overall speed of the hard disk bottleneck. Today, the mainstream of the brand's hard drive, the capacity of almost, the average seek time difference is small, the speed is also more than 7200 rpm, high-speed cache of about 2MB, the external data transfer rate are used UltraDMA100 technology, but the internal data transmission rate because of the brand and model different and presents a larger difference. Do not ignore the internal data transmission rate of concern when purchasing a hard disk.

Data transmission rates are divided into external transmission rates (External transferrate) and internal transmission rates (Internal Transfer Rate). The external data transfer rate refers to the speed at which the data is exchanged between the hard disk's cache and the system main memory, and the internal data transfer rate refers to the speed at which the disk head reads and writes data This metric often uses MB/s or Mbps, which is the meaning of Gigabit/sec, and if you need to convert to MB/s (Megabytes/sec), you must divide the Mbps data by 8 (byte digits). For example, the maximum internal data transfer rate is 240Mbps, but if you calculate by MB/s only 30mb/s, far from the hard disk interface 100mb/s. Therefore, the internal data transmission rate of the hard disk has become the bottleneck of the whole system bottleneck, only the internal data transmission rate of the hard disk has been improved, and then the interface speed of the hard disk is really meaningful.

4. Interface mode

Now commonly used hard disk is basically the DMA 100/133 or SATA, SCSI interface mode. Be aware that there are three SCSI hard disk interfaces, 50, 68, and 80 pins respectively. We usually have the hard disk model labeled "N" "W" "SCA", which means the number of interface pins. n namely narrow mouth (narrow), 50 stitches; W is wide mouth (Wide), 68-pin; SCA is single connectorattachment, 80-pin. One of the 80-pin SCSI disks generally supports hot-swappable.

5. Cache

The size of the cache has a greater impact on the speed of the hard disk, of course, the larger the better, at present the largest has reached more than 8MB. Should not be less than 2MB.

6. Safety

Hard disk as the main place to store information, the value of stored information is often much higher than the value of its products, the stability of the hard disk is very important. This should pay attention to the brand's reputation and whether to use the previous mentioned SPS and other data protection technology.

(three), the purchase of hard disk should pay attention to other issues

1, mean Latency (averagelatency): Refers to the time when the head is moved to the track where the data is located, and then waits for the desired block of data to continue to rotate (half circle or more, less) to the head, in milliseconds (ms).

2, Road to Road Time (Singletrackseek): Refers to the head from one track to another track time, in milliseconds (ms).

3. Full access Time (Maxfullseek): The unit is also milliseconds (ms), the total time that the head begins to move until it finally finds the required block of data.

4, average access Time (averageaccess): Refers to the head of the specified data to find the average time, in milliseconds (ms). Usually the sum of the average seek time and the average latency time. Note: Now many hard disk ads in the average access time is said to be replaced by the average seek time.

5, burst data transmission rate (Burstdatatransferrate): Also called the external data transfer rate (externaldatatransferrate), the unit is MB/s. Refers to the maximum rate at which the computer reads data from the internal buffer of the hard disk through the data bus. The data interface rate is often substituted in the ad or Hard disk feature table.

6, MTBF (continuous no fault time): Refers to the hard drive from the start to the failure of the maximum time, units are hours. The MTBF of a general hard drive is at least 30000 or 40,000 hours. This indicator in the general product advertising or the common technical characteristics of the table is not provided, when necessary, can be dedicated to the Internet to specific production of the hard disk of the company Web site query.

7, the single disc capacity: High disk disc capacity can at least bring us two major benefits: one is to make the hard disk can have a larger storage capacity. We know that the 3.5-inch hard drive can only install four discs, if you want to increase the storage space of the hard disk, the only way is to improve the single disk capacity. Increase the capacity of a single disc, with the same number of discs can produce a larger capacity of the hard disk, can further control the cost of the hard disk. The second advantage is that it can effectively improve the internal transfer rate of the hard drive. In the case of disk speed and the operation speed of the head, it is certain that the disk can be accessed by the head at the same time. and the single disc capacity increased, the data density on the disc is higher, the amount of data recorded on the unit area can be increased, the corresponding in the unit time the head can access to more data information.

8, heat and noise problems. The surface temperature of the hard disk refers to the temperature of the hard disk sealing shell when the hard disk is working. This indicator is not provided by manufacturers, generally can only be seen in a variety of media testing data. The high temperature produced by the hard disk will affect the data reading sensitivity of the thin film head (including Mr Head), so the hard disk with lower temperature of the working surface has better data reading and writing stability. If the heat emitted by the hard drive can not be transmitted in time, hard disk will be a sharp heating up, on the one hand will make the hard drive circuit work in an unstable state, on the other hand, the disk and the magnetic head for a long time in the high temperature can easily make the disc read and write errors and bad way, but also on the hard disk life will have some impact. Fortunately, with the development of technology, the market today, most of the heat of the hard drive has been gradually smaller, this point does not need to worry too much now. Noise does not have a big impact on a single hard drive. But in the dead of night, sometimes heard from the chassis in the bursts of hard disk noise, the sound is too loud, you will be upset and uneasy. Of course the more "quiet" hard drives are more popular.

9, overclocking problem. To stabilize overclocking, in addition to the CPU, other devices are also determined whether the stability of overclocking factors, hard disk is one of them. In many cases, not overclocking, is often caused by the hard drive. In particular, under non-standard FSB, the hard disk data transmission rate will also rise, the hard disk itself can not withstand, there may be abnormal phenomena, such as the inability to enter windows, and more serious will get data loss, the system is destroyed. So you are going to take the machine to overclocking friends to buy when you must consider this point.

For the 66MHz bus, when the bus frequency is over 75, 83MHz, the IDE bus will be overloaded 13.6%, 25.8% of the frequency operation; for 100MHz bus, the IDE bus will overload 124, 12%, 24% when it is over 112, 33, 133MHz. % of the frequency run. As a result, overclocking's hard drive can be harsh enough to be fatal, and failure can damage data and physical media on your hard drive.

10, fake problem. Strictly speaking, the hard disk product does not exist the problem of fakes. But there are still a few dealers in the market who often cheat on their hard drives. First, the old generation of products to the price of new products sold to users; second, the market on the hard drive, may be due to transport or other aspects of the problem, the small part of the quality may have some flaws (such as a small number of bad way), and some dealers will sell these products to those who do not know the user, On the one hand, infringing the legitimate rights and interests of users on the other hand, for the user's use of buried hidden dangers, the third is the problem of parallel imports, there are some of the market has not been normal customs clearance of hard disk, is what we usually call "parallel", it is said that these products and those who pass the normal customs formalities of the same model hard disk There is no difference in quality, but because of its special "channel", these products do not have a reliable warranty, although more than the normal channel of the same products cheaper, but "three-year warranty" into a "one-year warranty", some dealers although these products have made a "quality assurance three years" commitment, but this is not possible to be implemented, Users should avoid buying this type of product.