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Thursday, March 7, 2019

What is the difference between a solid state drive and a USB flash drive?

The working principle of SSD and U disk is the same, it is the main control chip + FLASH storage chip. However, many people have doubts. It is also the thing made by flash memory. Why is the speed of U disk never catch up with SSD? What is the difference between SSD and U disk? In fact, there is a big difference between the two, the following small series will give you a brief talk.


Why is the U disk speed never catching up with the SSD?

  We all know that a large number of U disk drives have adopted the faster USB 3.0 or even USB 3.1 interface, and its performance improvement is self-evident. For example, SanDisk's high-end U-disk SanDisk CZ880 uses a USB 3.1 interface with a maximum read speed of 420MB/s and a write speed of 380MB/s. But even if it has reached this level, it is still a lot worse than the popular M.2 SSD. The reason for this is that their main control algorithm is different !

  SSDs use a special algorithm, which is different for each manufacturer and is packaged in the main control chip. Through this algorithm, the data can be evenly distributed to each piece of flash in the solid state hard disk, which greatly increases the life of the flash while increasing the speed.

  More efficient algorithms can perform high-speed compression and reading of data, especially the reading speed can be very high, and the more efficient algorithm may be flat, but it can greatly extend the life of the FALSH chip. The problem of four or five years is not big. In addition to the main control algorithm, there is a big difference between the SSD and the U disk - the

life can be greatly extended.

  We also know that the U disk problem is frequent, because the U disk is a FLASH chip, high-end Two pieces. Repeatedly storing the same storage unit on a chip will speed up the aging of the chip, while the chip on the SSD is far more than one piece, two pieces, but up to dozens of chips. Through the coordination of the master control, the data is not distributed to different chips. In operation, the amount of operation of each chip is balanced, and the number of reading and writing of all the chips is superimposed in an invisible manner, which greatly prolongs the stable working time.

You can simultaneously read and write

  at the same time copying a file from the hard disk to the U disk and copying a file from the U disk to the hard disk. Compared with the speed of copying files to the U disk or the hard disk, the speed is much slower because the FLASH chip has the same storage. The unit structure can only read or write this single operation at the same time.

  FLASH reading and writing data is done by voltage change. Reading requires a voltage, writing a voltage, it is impossible to generate two kinds of voltages at the same time, but if there are many chips, the data is spread out, then for a chip combination. It is possible to read and write at the same time.


The quality of granules and chips is

  now a lot of counterfeit U disk on the market, but counterfeit SSDs are rare. This is because of the technical requirements of SSDs. If you want to make a fake U disk, you go directly to the Internet. Buy a fake master chip, plus even a polished Flash, solder and brush a master can form a USB flash drive.

  If you want to make a solid state drive, if you don't have strong research capabilities, the master level can't be overkill: you need to coordinate the reading and writing of multiple chips; you need to deal with the relationship between the data cache and Flash; Multiple channels can read the written skills at the same time.

The main control chip is not the same as the

  U disk and solid state hard disk structure principle, the main control chip + FLASH storage chip , but the main control chip of the U disk is a compact version. The sata controller has been removed, but controllers common to mobile devices such as zif (ce), esata, and usb are reserved. It is said that the addressing capability is also simplified, and now only a maximum of 8 FLASH chips can be achieved.

  The main control chip of the SSD supports less than 16 FLASH chips, and more than 32 FLASH chips, and even more. In addition, SSDs of the same brand and series usually have a situation where the larger the capacity, the faster the speed. Because, as mentioned above, a master chip controls 16 or 32 FLASH chips for simultaneous read and write operations, similar to the array concept of mechanical hard disks.

  The above is the difference between SSD and U disk. In general, they all use FLASH chip storage technology, but there are great differences in the main control algorithm, life extension and simultaneous reading and writing.

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