Shulou(Shulou.com)11/24 Report--

Many friends only know that solid state drives are "faster" than mechanical drives.

But where on earth is "fast"?

Why solid state drives are faster than mechanical drives?

In fact, it is the completely different working principle of solid-state hard drive and mechanical hard disk that determines the speed difference between them.

Let's study together today.

1. The working principle of mechanical hard disk the internal structure of mechanical hard disk is mainly composed of motor, magnetic disk, magnetic head arm and magnetic head.

When the mechanical hard disk is working, the magnetic head will be suspended a few nanometers above the disk surface. There are many small grids on the disk surface, and there are many small magnetic particles in the small grid.

The magnetic particles on these disks have a certain polarity, which is recorded as 0 when the magnetic particle polarity is down and 1 when the magnetic particle polarity is up, so that the magnetic head can read data by identifying the polarity of the magnetic particles on the disk.

The magnetic head can also use its changing magnetic field to change the polarity of magnetic particles on the disk, so that the disk data can be written and rewritten.

In order to accurately locate the position of the disk on which the data is located, the disk itself is divided into numerous sectors and tracks.

Suppose:

The data is stored on the seventh sector of track 5 of the disk:

The head will swing over track 5 and wait for sector 7 to turn around. The data can only be read when the seventh sector is transferred under the head.

This is how the mechanical hard disk works, and it is precisely because the mechanical hard disk uses magnetic poles to store data, so the mechanical hard disk is often called the disk.

The working principle of solid-state hard disk is completely different from that of mechanical hard disk. Solid-state hard disk adopts pure electronic structure.

2. The working principle of solid-state hard disk the basic unit of solid-state hard disk data storage is called floating gate transistor, and the basic structure is as follows: floating gate layer for storing electrons, control electrode G, substrate P, source D and drain S.

We count the number of electrons in the floating gate layer as 0 above a certain value and 1 below a certain value.

So how exactly does a solid state drive work? Keep looking down ~

When writing data to write data, a high voltage needs to be applied to the control pole G so that electrons can pass through the tunneling layer and enter the floating gate layer. because of the existence of the insulating layer, the electrons can no longer move forward and are imprisoned in the floating gate layer.

And when we remove the voltage, these electrons are still trapped in the floating gate layer, because the tunneling layer is essentially an insulator, so the electrons can only be held, so a bit of data is stored.

How long these electrons can be "imprisoned" is the number of years that a solid-state hard drive can store data, and a new solid-state hard drive can store data for 10 years. Because with the passage of time, there are continuous electronic "jailbreak" success.

When there are a certain number of electrons in Prison break, the data we keep will be gone.

Erasing data when we erase data on solid state drives, we are actually releasing these poor electrons, that is, putting high pressure on the substrate, so that the electrons are sucked out and the information is erased.

Through the above description, we learned about the process of writing and erasing data.

So how do you read the data?

Reading data about how it reads data is also very simple.

When there are no electrons in the floating gate layer (the storage data is 1), we give the control stage a low voltage. Because of the low voltage, the electrons can only be attracted to the position close to the tunneling layer, but cannot pass through the tunneling layer, so the source and drain can be conducted to form a current.

If a current is detected, then it does not store electrons, and the read data is 1.

When there are electrons in the floating gate layer (the storage data is 0), we also give a low voltage to the control electrode. because the electrons in the floating gate layer repel these electrons, the electrons cannot be attracted to the position close to the tunneling layer. the source and drain will not turn on and will not form a current.

If the current cannot be detected, then the floating gate layer stores a certain amount of electrons, and the read data is 0.

Countless floating gate transistors can be stacked together to store a large number of zeros and 1s, similar to the bookshelves in the library, storing unlimited 0101 data.

Compared with the mechanical structure of mechanical hard disk, the pure electronic structure of solid-state hard disk has a very outstanding advantage in terms of access speed.

Before the mechanical hard disk reads the data, it is necessary to swing the head arm above the corresponding track, and then wait for the corresponding sector to turn around.

Although most of the current mechanical hard drives are 7200 rpm or 5400 rpm, which seems to be fast, these two operations can still cause a delay of about ten milliseconds.

This delay is negligible for humans, but it does have a significant impact on computer memory and CPU.

The solid-state hard disk is full of electronic interaction, and the speed of electronic signals is much faster than the mechanical structure of magnetic head arm and disk.

If your data is randomly scattered in every corner of the disk, the mechanical hard disk needs to go through many times of seeking and addressing, waiting for the sector to rotate under the magnetic head many times, so the performance of the mechanical hard disk appears to be very weak when reading decentralized files. The speed is very slow, that is, the performance of random read and write is low.

After understanding the principle of solid state hard drive

You must know why solid state drives have a limit on the number of erasures.

Because in the process of floating gate transistor erasing, electrons repeatedly enter and exit in the tunneling layer, resulting in the damage of the tunneling layer, which can not effectively block electrons and lose the due role of the tunneling layer.

This article comes from the official account of Wechat: ZTE document (ID:ztedoc), author: ZTE document

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