How about QLC particles? Comparison knowledge of solid state hard disk QLC, SLC, MLC, TLC particle difference

Nowadays, solid state drives are developing rapidly, and the technology is gradually mature. The choice of solid state drives is no longer as simple as capacity selection. More people are more concerned about performance and particle types. For SSD particle types, I believe many users are right. QLC, SLC, MLC, TLC particle types are unknown, and especially for the latest solid state drives equipped with QLC particles, many users say that QLC particles are not good. So what about QLC particles? Next, Xiaolong, the home of the installation, will share the knowledge of the comparison of solid state drives QLC, SLC, MLC, and TLC particles.

According to the difference of electronic cell density in NAND flash memory, it can be divided into SLC (single-level storage cell), MLC (double-layer storage cell), TLC (three-layer storage cell) and the newly launched QLC (four-layer storage cell). Solid state drives rely on flash memory chips to store data. The smallest unit for storing data is called “Cell”. Each cell of SLC can store 1 bit of data, each cell of MLC can store 2 bits of data, each cell of TLC can store 3 bits of data, and QLC can store data. Store 4bit data.

In order for Xiaobai to better understand the meaning, let me give you an example. We can regard the chip as a piece of paper filled with grids. The cell is equivalent to the grids on the paper, and the data is regarded as a soybean. In other words, the SLC scheme can only put one soybean in each grid, so the storage space is small. The MLC scheme can put two soybeans in each grid, and the TCL scheme can put three soybeans in each grid. In the scheme, each grid can store four soybeans, and the storage space is relatively large when the cost remains the same. You must know that this paper (chip wafer) is also very expensive, that is to say, if the same wafer is made into SLC, it will only have 128G, and if it is made into MLC, it will have 256G. If it is made into TLC, it will become 512G, and if it is made into QLC, we Can be made into a larger capacity, but the cost is the same.

Comparison of the difference between QLC, SLC, MLC, TLC particles

SLC (Single Layer Storage Cell)

The full name is Single-Level Cell, single-layer electronic structure, each cell can store 1bit data, SLC reaches 1bit/cell, the voltage change interval is small when writing data, the P/E life is longer, and the theoretical erasing and writing times are 100,000 However, due to the highest cost, SLC particles are mostly used in enterprise-level high-end products.

MLC (Double Layer Storage Cell)

The full name is Multi-Level Cell. It uses high and low voltage and differently constructed double-layer electronic structure. MLC reaches 2bit/cell, P/E has a long life, and the theoretical erasing and writing times are about 3000-5000 times, and the cost is relatively high, but It is also acceptable for consumer-level products, and is mostly used in household-level high-end products.

TLC (three-tier storage unit)

The full name is Trinary-Level Cell, a three-layer storage unit, which is an extension of MLC flash memory. TLC reaches 3bit/cell. Due to the higher storage density, the capacity is theoretically 1.5 times that of MLC, and the cost is lower, but the P/E lifespan is relatively low. To be lower, the theoretical number of erasing and writing ranges from 1,000 to 3,000, which is the mainstream flash memory particle currently on the market.

QLC (four-layer storage unit)

The full name is Quad-Level Cell, a four-layer storage unit. QLC flash memory particles have a higher storage density than TLC, and at the same time, the cost is lower than TLC. The advantage is that the capacity can be made larger, the cost is lower, and the disadvantage is That is, the P/E life is shorter, and the theoretical number of erasing and writing is only 150 times.

QLC, SLC, MLC, TLC particle comparison

Why are QLC particles bad?

The more data stored in each Cell, the higher the capacity per unit area, but at the same time it will lead to more different voltage states and more difficult to control. Therefore, the solid state of QLC particles is adopted. Although the capacity is larger and the price is cheaper, the stability is better. Poor, and the P/E life is low, and the speed is the slowest.


The biggest advantage of QLC NAND lies in its lower cost. A larger capacity SSD can be made at the same cost, and the capacity will no longer be limited. For QLC particles, 1TB capacity is a trivial matter, ranging from tens to hundreds of TB. Is the mainstream, the era of large-capacity solid state drives has begun. But for P/E life and speed, this is the biggest disadvantage of QLC particles. The formula for P/E life is the number of erasing times*capacity/the amount of erasing and writing per day/365, but the solid-state drive capacity of QLC particles is very large. , Assuming a 1TB QLC particle solid state drive, 100G is erased and written every day, that is, its lifespan = 1024*100/100/365, about 2.8 years, and the maximum number of writes is also theoretical, and the excess is not necessarily It is 100% broken. The key computer cannot be turned on every day, and there are also periods of rest. In addition, it is impossible to erase 100G every day, so there is no need to worry too much about its lifespan. Waiting for the solid state drive to break down, and the entire computer is obsolete.

QLC particles believe that many users will say that it is a technological retrogression, but for manufacturers, the current user demand for storage capacity has increased. At present, the large-capacity solid state drives of TLC and MLC particles are more expensive, and lower cost and larger capacity are In the future, it is believed that QLC particles will enable solid state drives to enter the era of large-capacity and low-cost.

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