Memory type
The type of the main memory of the drive determines the features of the distribution of information over hardware cells and the physical features of the cells themselves.
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MLC. Multi Level Cell memory based on multi-level cells, each of which contains several signal levels. MLC memory cells store 2 bits of information. Has optimum indicators of reliability, power consumption and productivity. Until recently, the technology was popular in entry-level and mid-range SSD modules, now it is gradually being replaced by more advanced options in the manner of TLC or 3D MLC.
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TLC. The evolution of MLC technology. One Flash Memory Triple Level Cell can store 3 bits of information. Such a recording density somewhat increases the likelihood of errors compared to MLC, in addition, TLC memory is considered less durable. A positive feature of the nature of this technology is its affordable cost, and various design tricks can be used to improve reliability in SSDs with TLC memory.
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3D NAND. In a 3D NAND structure, several layers of memory cells are arranged vertically, and interconnections are organized between them. This provides greater storage capacity without increasing the physical size of the drive and improves memory performance due to shorter connections for each memory cell. In SSD drives, 3D NAND memory can use MLC, TLC or QLC chips - more details
...about them are described in the corresponding help paragraphs.
— 3D MLC NAND. MLC-memory has a multilayer structure — its cells are placed on the board not in one level, but in several "floors". As a result, manufacturers have achieved an increase in storage capacity without a noticeable increase in size. Also, 3D MLC NAND memory is characterized by higher reliability than the original MLC (see the relevant paragraph), at a lower manufacturing cost.
— 3D TLC NAND. "Three-dimensional" modification of the TLC technology (see the relevant paragraph) with the placement of memory cells on the board in several layers. This arrangement allows you to achieve higher capacity with smaller sizes of the drives themselves. In production, such memory is simpler and cheaper than a single-layer one.
— 3D QLC NAND. Quad Level Cell flash type with 4 bits of data in each cell. The technology is designed to make SSDs with large volumes widely available and finally retire traditional HDDs. In the 3D QLC NAND configuration, the memory is built according to a “multi-level” scheme with the placement of cells on the board in several layers. "Three-dimensional" structure reduces the cost of production of memory modules and allows you to increase the volume of drives without compromising their weight and size component.
— 3D XPoint. A fundamentally new type of memory, radically different from traditional NAND. In such drives, memory cells and selectors are located at the intersections of perpendicular rows of conductive tracks. The mechanism for recording information in cells is based on changing the resistance of the material without the use of transistors. 3D XPoint memory is simple and inexpensive to produce, and offers much better speed and durability. The prefix "3D" in the name of the technology says that the cells on the crystal are placed in several layers. The first generation of 3D XPoint received a two-layer structure and was made using a 20-nanometer process technology.Write speed
The highest speed in write mode characterizes the speed with which the module can receive information from a connected computer (or other external device). This speed is limited both by the connection interface (see "Connector"), and by the characteristics of the device of the SSD itself.
Read speed
The highest data exchange rate with a computer (or other external device) that the drive can provide in read mode; in other words —
the highest speed of information output from the drive to an external device. This speed is limited both by the connection interface (see "Connector"), and by the characteristics of the device of the SSD itself. Its values can vary from 100 – 500 MB / s in the slowest models to 3 Gb / s and higher in the most advanced ones.
Shockproof
A parameter that determines the resistance of the drive to drops and shocks during operation. Measured in G — units of overload, 1 G corresponds to the usual force of gravity. The higher the G number, the more resistant the device is to various kinds of shocks and the less likely it is to damage the data in it, say, in the event of a fall. This parameter is especially important for external drives (see Type).
Write IOPS
The IOPS provided by the drive in write mode.
The term IOPS refers to the highest number of I / O operations that an SSD module can perform per second, in this case, when writing data. By this indicator, the speed of the drive is often evaluated; however, this is not always true. Firstly, the IOPS values of different manufacturers can be measured in different ways — by the maximum value, by average, by random write, by sequential write, etc. Secondly, the benefits of high IOPS become noticeable only with some specific operations — in in particular, the simultaneous copying of numerous files. In addition, in fact, the speed of the drive may be limited by the system to which it is connected. In light of all this, it is generally acceptable to compare different SSD modules by IOPS, but the real difference in performance is likely not to be as noticeable as the difference in numbers.
As for specific values, for the write mode with IOPS
up to 50K is considered relatively modest,
50 – 100K — medium,
more than 100K — high.
