The main technical indicators of hard disk include?

I prefer Seagate, but the price is a bit expensive. Just look at the introduction below.

Hard disk performance technical index

Now, we often see the storage capacity of each hard disk from advertisements or magazines and newspapers. The interface is ATA 100, and the data cache is 4MB. Will these indicators affect the performance of the hard disk? What are the technical indicators that affect the performance of hard disks? The author made a statistic, which is listed as follows:

1, speed

Undoubtedly, the rotational speed is the most noticeable performance parameter besides the hard disk capacity. When any hard disk comes out, the first article of its promotional materials will mention its speed. The rotational speed has a great influence on the instantaneous transmission speed and continuous transmission speed of hard disk. I have a special discussion on its mechanism in the first issue of this journal, so I won't go into details here. At present, IDE hard disks mainly have two series: 5400 rpm and 7200 rpm.

2. The storage capacity of each disk

If rotational speed is the first factor of hard disk performance, then the second factor is undoubtedly the magnetic recording density on the disk surface. Because at present, the desktop IDE hard disk shell can only hold four discs, and only IBM can hold five discs. Obviously, it is not feasible to expand the capacity by adding more disks to meet the growing demand for storage capacity. Only by increasing the capacity of each disk can this problem be fundamentally solved. The standard size of desktop IDE hard disk is 3.5 inches (disk diameter), so the density of magnetic recording must be increased. However, with the increase of disk density, the magnetic head must become more and more sensitive. The maximum single disk storage capacity of traditional MR heads is about 4.5G At present, all hard disks with single disk storage capacity exceeding 5G have used GMR heads.

In addition to the contribution to capacity growth, unit disk storage has another important significance in improving the data transmission speed of hard disk. The increase of storage capacity per disk benefits from the increase of track number and linear magnetic density in tracks. The increase in the number of tracks is of great benefit to reducing the seek time of the magnetic head, because the radius of the magnetic sheet is fixed, and the increase in the number of tracks means that the distance between tracks is shortened, and the positioning time required for the magnetic head to transfer from one track to another is shortened. This will help to improve the speed of random data transmission. The increase of linear magnetic density in the track is directly related to the continuous data transmission speed of the hard disk. Because the current IDE hard disk does not need interleaving factor, every time the disk passes under the head, the target data of the track where the head is located will be read once. With the increase of track linear density, more data can be stored in each track, so that more data can be read from the head to the buffer of the hard disk in each circular motion of the disk. The new generation of GMR head technology ensures that this growth will not be slowed down because of the sensitivity limitation of the head. This is why many times, a 5400RPM hard disk with a high storage capacity per disk has higher performance than a 7200RPM hard disk with a low storage capacity per disk.

Therefore, the storage capacity per disk is the second largest performance parameter after the rotational speed, which directly determines the continuous data transmission speed of the hard disk. The most obvious gap between different generations of products in the 5400RPM and 7200RPM series is the storage per disk.

3. average seek time

This is the average time for the head to reach the track where the target data is located. This time, together with the average delay of the head (completely determined by the rotation speed), determines the time for the hard disk head to find the cluster where the data is located. This time directly affects the random data transmission speed of the hard disk. In addition to the storage capacity per disk mentioned above, the average seek time of the magnetic head is mainly determined by the operating speed of the magnetic head power arm. At present, among the mainstream hard drives, except Seagate's ATA Cool Fish is 7.6 milliseconds faster. The mainstream models of other brands are basically 8.5 ~ 9 milliseconds.

4. Data caching

In addition to the three factors mentioned above, increasing the capacity of hard disk cache is also a shortcut to improve the overall performance of hard disk.

Because the data transmission speed inside the hard disk (data from the disk to the cache) and the interface transmission speed (data from the hard disk cache to the system main memory) are different. Therefore, cache is needed to make speed adapters. Cache mainly improves the performance of hard disk from the following two aspects:

In the process of data reading, the control chip in the hard disk sends an instruction to read the data of the next cluster or adjacent cluster being read by the system instruction into the hard disk cache. When the system instructs to start reading the data of the next cluster, the hard disk does not need to start reading again, but only needs to transfer the data in the cache to the system main memory. Because the data transmission from the hard disk cache to the main memory of the system is only an electronic action, the speed is much faster than the mechanical action required for hard disk reading. Because the storage of data on disk is relatively continuous, the hit rate of this kind of pre-reading next cluster is very high. The increase of cache capacity can accommodate more pre-read data.

In the operation of writing data to disk, the data will first be written from the main memory of the system to the cache. Once this operation is completed, the system can move to the next operation instruction without waiting for the operation of writing the data in the cache to disk to be completed. This greatly shortens the waiting time of the system. With the increase of cache capacity, more system waiting time is saved. Therefore, the size of the buffer has a great influence on the continuous data transmission speed of the hard disk. Therefore, at present, the cache of mainstream hard disks on the market has almost increased to 2M. New products launched by various companies deliver product positioning to the market through cache capacity. 2M cache display is the mainstream model, and 5 12K cache is undoubtedly a cheap model positioned in the low-end market.

5. Interface type

Interface is also an important factor affecting the performance of hard disk, which directly affects the maximum external data transmission supported by hard disk. At present, the mainstream hard disk interface type is Ultra ATA/66, and the latest ATA interface is Ultra ATA/ 100. Since 1998 put forward Ultra ATA/66 interface standard, almost all newly introduced IDE hard disks now support DMA66 without exception. However, due to the limitation of hard disk platter and disk technology, the current internal data transmission rate and continuous data transmission rate of hard disk can not reach 66MB/s, and the transmission rate of general hard disk is between 35 MB/s and 45 MB/s, so the full effect of Ultra ATA/66 can not be fully exerted so far.

6. Data protection mechanism

With the increase of hard disk capacity and speed, people have higher and higher requirements for hard disk security. Therefore, various companies have developed data protection systems.

One of the most distinctive features is the data guardian of Western Digital. This technology is based on S.M.A.R.T., but it is independent of S.M.A.R.T. The specific working process is somewhat similar to Microsoft's ScanDisk ("Data Guard" technology is fully compatible with S.M.A.R.T. and ScanDisk), but it is more automatic: the hard disk can automatically detect and repair the wrong data after being powered on for 8 hours. If the scanning process is interrupted due to the system's resumption of work or shutdown during the scanning process, the hard disk will continue scanning after the system is idle again (or idle after startup) 15 seconds until the task is completed. It takes only 8 minutes for the 4.3G hard disk to be fully scanned, and 20 minutes for 13G hard disk, which is a good assistant to protect hard disk data.

In addition, there are DFT (drive adaptation test) of IBM, DPS (data protection system) of Quantum, MaxSafe of MAXTOR and anti-collision design of Seagate up to 300G. These protection mechanisms are similar.