At present, U disk with USB 3.0 or even USB 3.1 interface is not a minority, high-end U disk even breaks the reading and writing speed of 300MB/S. U disk can have such a good result, but compared with SSD There are quite a few gaps. So are the flash memory why the gap between U disk and SSD is still so different?
There is a difference in the master
U disk not only has the main control but also is divided into two major types of main control, the first one is the ordinary USB main control, straight through the flash granules, controlled by the USB main control chip, the U disk usually does not exceed 100MB/s. The read and write speed, such as the main control type of U disk bit width are 8-16bit, the performance will not go up.
The other is to use SSD master, which is more common on high-end U disk, and the SATA interface is formed by USB transfer. Many SSD master chips are actually operating units above the 32-bit reduced instruction set processor architecture, which can be seen on many mobile devices.
Speaking of this, everyone still understands the difference in price and speed behind high-end USB flash drives and ordinary USB flash drives. Since the high-end U disk also uses the SSD main control chip, why is the access speed still not comparable to the SSD? There are two main points in the SSD that are not restrictive. When the high-end U disk is transferred to the USB through the SATA interface, this will lose some of the read and write performance to some extent. The upgrade from USB 3.0 to the USB 3.1 interface can still restore some performance.
Compressed and uncompressed algorithms
The U disk master algorithm has two compression and non-compression algorithms, the biggest difference is that the write amplification ratio is different. The compression algorithm master recognizes the data, the processor performs a certain proportion of compression for the "compressed data", and then writes the compressed data into the flash memory, which is beneficial to reduce the data write amount of the flash memory; the non-compression algorithm master does not Differentiating data types and writing data directly to flash memory speeds up the life of flash memory.
Both compression and non-compression algorithms have advantages and disadvantages. The compression algorithm helps to extend the life of the flash memory. The read and write performance is relatively superior in the face of compressed data, but the performance is not good when reading and writing uncompressed data. In contrast, the non-compressive algorithm, which takes into account both compressed and uncompressed data, has stable performance, but has high requirements for flash quality. This non-compressive algorithm generally does not appear in small-capacity SSDs or U-disks. In the storage, because the number of reading and writing of the device does not support such a high read and write speed.
Most high-performance U diskes will not be lower than 64GB-1TB capacity, and large capacity supports non-compressive algorithm mastering, thus achieving good performance under non-compressed algorithms. The two barriers of conversion and mastering obviously make the USB interface U disk catch up with the speed of the SSD become a less realistic idea, but they are all in the same memory, and you want to use SSD storage for speed.