Are flash memory U disk without SSD fast?

Now many U-disks, especially high-end U-disks, have adopted USB 3.0 or even USB 3.1 interfaces, and the performance is indeed a lot better than before, and some have even exceeded 300MB/s read and write speeds. However, they are all made from flash memory. Why is U disk speed not catching up with SSD?

For example, the very high-end U disk products HyperX Savage and SanDisk CZ880, are all using USB 3.1 interface, the maximum speed reached 350MB/s read 180Mb/s write and 420MB/S read 380MB/S write, enough amazing it ? However, compared to high-performance SSDs, the gap is quite large (actually faster than Xiaobian's antique SSD...), which is largely a matter of mastermind.

U disk also has master it? Of course, at present U disk is divided into two main types of control, one is the ordinary USB host, through the flash memory particles, through the USB master chip control, but the bit width is relatively low, only 8bit ~ 16bit, the performance will naturally not I think, usually the performance of this U disk is 100MB/s read and write.

The second is a relatively high-end U disk, they use SSD master control, the interface is actually SATA, and then through the SATA to USB adapter born. It should be noted that the SSD master chip is actually an operating unit with a 32-bit ARM architecture level and the performance is naturally much higher.

The U-disks that traditionally use USB hosts do not have much to say here. They mainly talk about the advanced U-disks of SSDs. Logically speaking, the same as the main chip with SSD, why not catch up with the speed of SSD hard disk?

There are actually two things that affect the performance of using SSD master U disk. The first is just mentioned, SATA to USB transfer this conversion process, will largely lose part of the read and write performance, just like the two U-disk examples Xiaobian move well, if not using the USB 3.1 interface, they The performance will be further reduced (a laptop running on a USB 3.0 interface will run for a minute).

The second relates to the SSD master control algorithm used by U disk. Many small partners know that SSD master control is now divided into two camps. One is a compression algorithm and the other is a non-compression algorithm. The biggest difference between these two algorithms is the write amplification ratio. The main algorithm of the compression algorithm identifies the data. The processor compresses the compressed data according to a certain proportion. Then the compressed data is written into the flash memory, which is beneficial to reduce the data writing amount of the flash memory; the main control of the non-compression algorithm is not Differentiating data types and writing data directly to the flash memory has a higher requirement on the lifetime of the flash memory.

The advantage of the compression algorithm is that it helps to prolong the service life of the flash memory. For compressed data, it can exhibit a higher level of performance. The disadvantage is that when reading and writing non-compressed data, the performance must be reduced; the main part of the non-compression algorithm is The advantage of control is that it consumes both compressed and non-compressed data and maintains the original reading and writing performance. However, the disadvantage is that it requires high quality of flash memory and it is impossible to apply it to small-capacity storage (SSD or U disk). , otherwise such a high read and write speed will quickly allow the device to read and write the maximum number of times.

So you can see that the high-performance U disk starts with 64GB at the very least until 512GB/1TB, and most of them choose the non-compression algorithm to achieve the best performance.

Obviously, a bridging conversion and a master control algorithm are the basic reasons that affect the reading and writing speed of high-performance U disk. To a certain extent, U disk with USB interface is almost impossible to catch up with SSD. The partner who has this idea can give up.