Not all M.2 are NVMe:SSD literacy guide.
SLC, MLC or TLC?
I believe that some players who know a little about SSD have heard about SLC, MLC and TLC, and their impression of TLC should be synonymous with poor performance and short life. SSD relies on NAND Flash memory chip to store data, which is very similar to the U disk we use in principle. According to the storage principle of NAND Flash, SSD can be divided into SLC(Single-Level Cell), MLC(Multi-Level Cell) and TLC(Trinary-Level Cell).
In principle, SLC only stores 1bit of data in each memory storage unit, and there are only two charging values, 0 and 1. MLC stores 2 bits of data in each memory storage unit, and has four charging values of 00, 01, 10 and 11. It takes more time to access data than SLC, but its advantage is that it has higher data density and can reduce production costs. TLC stores 3 bits of data in each memory storage unit, and there are 8 charging values. In the process of use, in order to meet these 8 different voltage states, the main control chip needs to apply different voltage states, which takes longer to complete, and the result is slower access speed. However, the advantage of TLC is that it has the highest data density and the lowest cost, and it is also very easy to make a large-capacity SSD at a competitive price segment.
TLC is obviously different from MLC in life and performance.
Players talk about the color change of TLC, among which the slow reading and writing speed is not the main reason, and what is more worrying is the life of TLC SSD. Compared with MLC with 3000+ times and SLC with nearly infinite life, the theoretical erasure life of 1000 times is so short.
More advanced technology will make the original more fragile.
The former principle part briefly explains the working state of TLC SSD when it is used. With the development of semiconductor technology, the thickness of insulator silicon oxide is getting thinner and thinner. Every time SSD is written and erased, the process of applying voltage itself has physical losses. In addition, TLC needs to handle eight different voltages at the same time. The physical laws determine that electrons may be stranded in the silicon dioxide insulation layer. This will make each erasing time longer than the last time. With the longer use time, it will take longer and higher voltage value to reach the original voltage every time. The main control chip will also try different voltages when it detects that the original design voltage value is abnormal, which will further slow down the speed and bring further losses.
Why TLC is dominating SSD market?
Whether you want to admit it or not, although the players have a bad reputation for TLC, the SSD market is inevitably dominated by TLC SSD. Are products with obvious shortcomings such as short life and poor performance released to the market by major manufacturers just because of low cost?
In fact, the reason why TLC SSD now occupies most of the market share is that manufacturers have found a solution to the slow reading and writing speed and short life of TLC.
More components are accommodated through the multilayer stack structure.
First of all, the life-span problem is solved thanks to the 3D NAND structure. The original 2D NAND pursues smaller memory cells through more advanced semiconductor technology in exchange for larger storage capacity, which aggravates the short life-span problem for TLC. However, the idea of 3D NAND structure has changed, instead of pursuing smaller units on a plane, more units are put down by stacking and packaging, so the space saved can use relatively old processes. The advantage of using the old process is that the number of P/E erasures is greatly increased, and the situation of charge interference is also greatly reduced because of using the old process.
In recent years, the improvement of the main control chip by the manufacturer has further improved the service life of TLC, and has made progress in signal processing, algorithm and so on. So that today’s TLC SSD can also be on par with MLC in quality assurance.
Use part of TLC in SLC mode.
TLC belongs to a state of "treating the symptoms but not the root cause" in solving the speed problem. In principle, it is determined that the reading and writing speed of TLC can’t be faster than MLC or even SLC, but we don’t always read and write data with a very large amount of data. By turning a part of TLC into a cache area, manufacturers make it simulate the working mode of SLC, that is, SLC Cache (that is, 3 3bits are used as 1bit). In this way, it brings a small amount of data to read and write, and TLC also has a very fast speed.
When the buffer is full, it will restore the original speed of TLC.
It is said to be "temporary solution" because this method can’t keep TLC at a high speed. When the buffer is full, the reading and writing speed will be "exposed".
Players need to pay attention to buying mainstream regular manufacturers’ granules when purchasing SSD. The original granules are the best, white films can be considered, and black films should not be considered directly. Don’t be greedy for petty gains. The data is very valuable.
Main control chip
The main control chip in SSD can greatly affect its final performance and service life. In addition, the main control chip directly determines whether the SSD of M.2 interface takes SATA channel or PCI-E channel.
Main Control Chips Among the mainstream brands in the market, Samsung’s main control chips are often self-produced and sold, and only used in their own SSDs. The main control chips of other major main control manufacturers, such as Marvell, SandForce, Huirong, Qunlian, Zhiwei and Toshiba, are distributed in products of various price segments, and the performance of main control chips of products with different prices is almost the same. The main controller mainly controls the reading and writing of data and FTL layer algorithms (such as wear balance WL, garbage collection GC, etc.), which largely determine the performance of SSD. Players don’t have to worry too much about the specific performance of the main control when purchasing SSD, but they should avoid the "spelling the evening" main control chip:)