Hard disk performance indicators:

A, capacity

As a computer system data storage, capacity is the hard disk's most important parameter.

The capacity of a hard disk is measured in megabytes (MB) or gigabytes (GB), with 1GB=1024MB, but hard disk manufacturers usually take 1G=1000MB as the nominal capacity of the hard disk, so the capacity we see in the BIOS or when formatting the hard disk will be smaller than the manufacturer's nominal value.

The capacity of a hard drive also includes the capacity of the drive's single disk. Single-disk capacity refers to the capacity of a single platter on a hard drive. The larger the single-disk capacity, the lower the unit cost and the shorter the average access time.

Two, rotational speed

Rotation speed (Rotationl Speed or Spindle speed), is the hard disk motor spindle rotation speed, that is, the hard disk platters in a minute to complete the maximum number of revolutions. Rotation speed is one of the most important parameters for labeling the grade of a hard drive, and it is one of the key factors in determining the internal transfer rate of a hard drive, which directly affects the speed of the drive to a large extent.

The faster the speed of the hard disk, the faster the hard disk can search for files, and the relative transfer speed of the hard disk is also improved. The speed of a hard disk is expressed in revolutions per minute (RPM), which stands for revolutions per minute, and the larger the RPM value, the faster the internal transfer rate, the shorter the access time, and the better the overall performance of the hard disk.

Three, Average Access Time

Average Access Time (Average Access Time) is the time it takes for the head to reach the target track location from its starting position and to locate the data sector to be read or written from the target track.

Average Access Time reflects the read/write speed of a hard disk, which includes the seek time and wait time of the hard disk, i.e.: Average Access Time = Average Seek Time + Average Wait Time.

The average seek time (Average Seek Time) of a hard drive is the amount of time it takes for the drive's heads to move to the designated track on the platter. This time is of course the smaller the better, the current hard disk average seek time is usually between 8ms to 12ms, and SCSI hard disk should be less than or equal to 8ms.

Hard disk wait time, also called latency (Latency), is the head has been in the to be accessed to the track, waiting to be accessed to the sector rotation to the head of the time below. The average waiting time is half of the time it takes for the disk to rotate one week, and should generally be less than 4ms.

Four, transfer rate

Transfer rate (Data Transfer Rate) hard disk data transfer rate refers to the hard disk read and write data speed, the unit is megabytes per second (MB/s). Hard disk data transfer rate includes internal data transfer rate and external data transfer rate.

Internal Transfer Rate, also known as Sustained Transfer Rate, reflects the performance of a hard disk when its buffers are unused. The internal transfer rate is largely dependent on the rotation speed of the hard disk.

External Transfer Rate, also known as Burst Data Transfer Rate or Interface Transfer Rate, is a nominal data transfer rate between the system bus and the hard disk buffer, and is related to the type of hard disk interface and the size of the hard disk cache.

V. Cache memory

Cache memory is a memory chip on the hard disk controller with extremely fast access speeds, which is a buffer between the hard disk's internal storage and the external interface. Since the internal data transfer speed of the hard disk is different from the transfer speed of the external interface, the cache plays a buffer role in it.

The size and speed of the cache is directly related to the transmission speed of the hard disk, which can greatly improve the overall performance of the hard disk. When the hard disk accesses fragmented data, it needs to constantly exchange data between the hard disk and the memory. With a large cache, the fragmented data can be stored temporarily in the cache, which reduces the load on the external system and improves the data transfer speed.

Expanded

Hard drive maintenance notes

1, read and write taboo power outage

Hard drive speed is mostly 5400 rpm and 7200 rpm, SCSI hard drive more in 10000 to 15000 rpm, in the read and write, the whole disk is in a high-speed rotating state, if the sudden If the power supply is cut off suddenly, it will make the magnetic head and the platters rub violently, which will cause the hard disk to appear bad or even damaged, and often cause the data stream to be lost.

So when shutting down your computer, be sure to pay attention to the hard drive indicator on the chassis panel to see if it's not blinking, i.e., the hard drive has already completed its read/write operation before shutting down the computer in accordance with normal procedures. When the hard disk light is flashing, you must not cut off the power supply. If it is a removable hard disk, it is best to perform a hardware security deletion first, and then unplug it after success.

2, maintain a good environment

Hard drive on the environmental requirements of the higher, sometimes serious collection of dust or air humidity is too large, will cause electronic components short circuit or interface oxidation, which causes hard drive performance instability or even damage.

3, prevent vibration

Hard drive is a very precise storage device, read and write operations, the magnetic head in the surface of the platter floating height of only a few microns; even when not working, the magnetic head and the platters are also in contact. Hard disk at work, once a large vibration, it is easy to cause the magnetic head and the data area collision, resulting in damage to the disk data area or scratch the disk, the loss of hard disk data stored in the file.

Therefore, do not move the computer or move the hard disk while it is working or before the spindle motor has stopped after shutting down the computer, so as to avoid the magnetic head colliding with the disk and scratching the magnetic layer on the disk's surface. In addition, in the hard disk installation and removal process should also be doubly careful to prevent excessive shaking or with the chassis iron plate violent collision.

4, reduce the frequent operation

If a long time to run a program (such as large-scale software or play games), or long-term use of BT and other download software, this time to pay attention to, so that the magnetic head of the long time frequently read and write the same hard disk location (i.e., the program is located in the sector), so that the hard disk to produce a bad sector.

In addition, if you use an operating system for a long time, you can also make the hard disk sector where the system files are located (non-removable) in a long-term read state, which accelerates the damage of the sector. Of course, it is best to have two or more operating systems installed and used interchangeably to avoid prolonged read and write operations to a particular sector of the hard disk.

Baidu Encyclopedia - Hard Disk Performance Indicators