Repost one of Hard Disk terms

1. Hard Drive Speed: rotationl speed

That is, the speed of the hard drive motor spindle. Speed is one of the key factors that determine the internal transmission rate of the hard disk. It also greatly affects the speed of the hard disk. At the same time, speed is also an important indicator of distinguishing hard disk grades. At present, common hard disks on the market are generally 5400 RPM (RPM) or 7200 RPM, and high-grade SCSI hard disks can reach 10000rpm or even 15000 rpm. Theoretically, the faster the speed, the better.

As the disk capacity increases, the speed of the hard disk is also increasing. However, the increase in rotation speed has also brought a series of negative effects, such as increased wear, increased temperature, and increased noise. Therefore, fluid dynamic bearing Motors Applied in the precision machinery industry are introduced into hard disk technology to effectively absorb vibration, reduce wear and improve service life.

2. Average seek time (average seek time)

It refers to the time used by the hard disk to move the write head on the disk to the specified track to find the corresponding target data. It describes the hard disk's ability to read data, in milliseconds. When the capacity of a single disc increases, the seek action and moving distance of the head are reduced, reducing the average seek time and accelerating the hard disk speed. At present, the average seek time for mainstream hard disks on the market is usually about 9 ms.

3. Average latent time (average latency time)

It refers to the time when the head moves to the track where the data is located, and then waits until the desired data block continues to rotate to the bottom of the head, generally 2 ms ~ Between 6 ms.

4. Average access time (average access time)

Indicates the average time of the head to locate the specified data, usually the sum of the average seeking time and average latent time. The average access time represents the time used to locate a data disk. The shorter the average access time, the better, generally between 11 ms and 11 ms ~ Between 18 ms. Note: Most of the average access times mentioned in many hard drive advertisements are replaced by the average seek time.

5. burst data transmission rate)

It refers to the maximum rate at which the computer reads data from the cache area of the hard disk through the data bus, also known as the external data transfer rate ). This parameter should theoretically be equal to the interface speed. For example, the hard disk of udma/66 should be 66 Mb/s, and the hard disk of udma/100 should be 100 Mb/s. But in fact, due to interface efficiency problems, this value is often more than 10% lower than the theoretical value.

6. Maximum internal data transmission rate (internal data transfer rate)

It refers to the maximum data transfer rate between the head and the hard disk cache, generally depends on the disk speed and disk data line density. Currently, the internal transmission rate of most hard disks is about 40 MB/s, but the maximum internal data transmission rate of a few hard disks has exceeded 50 MB/S. Because the internal data transmission rate is the real bottleneck of the system, therefore, we need to distinguish these two concepts when purchasing them. However, in general, the speed of the hard disk is the same, and the internal transmission rate of the single-disc capacity is high; while the single-disc capacity is the same, the internal transmission rate of the hard disk with high speed is high.