Size
Nominal drive capacity. This parameter directly determines not only the amount of data that can fit on the device, but also its cost; many SSD models even come in several versions that differ in capacity. Therefore, when choosing, it is worth considering the real needs and features of the application — otherwise you can overpay a significant amount for volumes that are not needed in fact.
In terms of actual values, a capacity of
120 GB or less is considered small these days. This can also be equated with
a 240 GB SSD. Average values are already considered
500 GB, increased —
1 TB(in the range of which
SSDs fall 400 and
800 GB). And the most capacious modern SSDs can accommodate
2 TB,
4 TB and
even more.
Controller
Model of the controller installed in the SSD.
The controller is a control circuit, which, in fact, ensures the exchange of information between the memory cells and the computer to which the drive is connected. The capabilities of a particular SSD module (in particular, read and write speed) largely depend on this particular scheme. Knowing the controller model, you can find detailed data on it and evaluate the capabilities of the drive. For simple everyday use, this information is usually not needed, but for professionals and enthusiasts (modders, overclockers) it can come in handy.
Nowadays, high-end controllers are produced mainly under such brands:
InnoGrit,
Maxio,
Phison,
Realtek,
Silicon Motion,
Samsung.
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.
—
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.
—
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.
—
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.
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.
TBW
The abbreviation TBW stands for drive time between failures, expressed in terabytes. In other words, this is the total amount of information that is guaranteed to be written (rewritten) to this module. This metric measures the overall reliability and lifespan of a drive—the higher the TBW, the longer the device will last, all other things being equal.
Note that knowing the TBW and the warranty period, you can calculate the number of rewrites per day (DWPD, see the relevant paragraph), if the manufacturer did not specify these data. To do this, use the formula: DWPD = TBW / (V * T * 365), where V is the drive capacity in terabytes, T is the warranty period (years). As for specific numbers, there are a lot of drives on the market with a relatively low TBW —
up to 100 TB ; even these values are often sufficient for everyday use for a considerable amount of time. However, models with TBW at the level
of 100 – 500 TB are more common. Values of
500 – 1000 TB can be classified as "above average", and in the most reliable solutions this figure
is even higher.
Manufacturer's warranty
Manufacturer's warranty provided for this model.
In fact, this is the minimum service life promised by the manufacturer, subject to the rules of operation. Most often, the actual service life of the device is much longer than the guaranteed one. However, keep in mind that the warranty often includes additional terms, such as “[so many years] or until the TBW is exhausted” (for more on TBW, see above).
Specific warranty periods may vary even for similar drives from the same manufacturer. The most popular options are
3 years and
5 years, however, there are other figures — up to
10 years in the most expensive and high-end models.
Data encryption
Data encryption ensures the protection of storing information on a disk: only someone who knows the password can access encrypted information. The encryption module is an integral part of the drive and does not depend on the computer to which it is connected. The ability to encrypt data is critical if you plan to write confidential information to discs; this feature is especially useful for portable drives and laptop drives, which are more at risk of theft than fixed systems and their components.
