There are two main reasons why U disk writes become slower and slower, one is cache and the other is temperature

First, let’s briefly introduce the characteristics of U disk, SSD storage, and store data in In terms of chips rather than mechanical structures, it is similar to solid-state drives and mobile hard drives. It uses electronic technology rather than mechanical technology to record information, so the speed and stability are very good (theoretically). With the development of technology, the most advanced U disk has actually been There is no problem of large changes in reading and writing speeds. The theoretical speed of the 3.0 interface has far exceeded the theoretical speed of the hard disk, which means that the reading and writing speed is actually limited by the hard disk or flash memory chip. Of course, this is based on the 3.0 interface, 2.0 and 1.0. The speed of the 1.1 interface is far lower than the hard disk speed.

Carefully observe the reading and writing speed of the U disk. Generally, the speed can reach 30M/s in the first few M to dozens of M (the actual writing speed of 3.0 is used as an example here and below), four or five seconds. Then it dropped to about 25M/s, and then it became about 18M/s in the next few minutes. At this point, it is basically the same or fluctuates slightly (if there is a big fluctuation, it is recommended to check the bad sectors of the hard disk)

The first deceleration , there are two reasons. The first is the writing speed in the cache. For example, the transmission station is like transporting something. In fact, the first movement of catching it will be very fast, and then it will slow down. The second reason is that the system reflects the speed, that is, the calculation speed will actually be performed later after the transfer starts (so the system above WIN8.1 calculates the speed first), which will cause a false speed bonus, just like downloading files on Thunder and getting stuck. After a few seconds, the speed display will soar, even exceeding the Internet speed.

The second reason is that the U disk is getting hotter and hotter.

Thermal resistance effect, the resistance value of the resistor will become higher at high temperatures, and the relative change rate will decrease. Most of them Electrical components have a similar effect, that is, their sensitivity is reduced under high temperatures.

The working temperature of flash memory chips is 0-70 degrees Celsius, and industrial grade can reach -40-85 degrees Celsius. If the U disk is not well designed and has poor heat dissipation, it may even be in danger of "burning out". The internal resistance of a U disk that works continuously at high temperature is very high, and the current is reduced, so it cannot "work at full strength". In fact, this is a kind of protection for the U disk. Some designs even add a resistor to ensure that it will not be damaged by excessive power. Here is a brief introduction to why it gets hotter and hotter. Generally, USB has a constant voltage of 5V. After operation, the resistance is heated. When most electrical components are heated, the resistance will increase (so there is no resistance in absolute zero substances). Constant voltage Multiplied by larger and larger resistances, you get more power, which snowballs and gets hotter and hotter until it reaches the temperature dissipation limit (the larger the temperature gradient, the faster the heat conduction) and the temperature remains constant. Therefore, the USB flash drive that has just been transferred will be very hot, so it is more efficient to let the USB flash drive "rest" after transferring a part of it.

Finally, there is another reason. This reason is taken out separately because it is not a USB flash drive, but a problem that all data transmission has. It is based on the WIN system (the higher the version, the more obvious it is) Estimates are made when transmitting big data. The estimated calculation amount increases with the number of files (not the file size). That is to say, transmitting a large file will be faster than transmitting multiple very small files or transmitting a file with many files. Folding is much faster, which involves the multi-threading capabilities of the system and processor, so it is best to package large files when transferring them (of course, transferring a folder is much better than opening multiple processes at the same time, and it is best to compress it into one file)