Hello friends. In this article, we will talk about the types of SSD storage. Now an active phase of the epochal change of generations of hard drives is taking place: due to the reduction in the production cost of SSD drives, obsolete HDDs are rapidly being sent to the dustbin of IT history.
But modern SSD hard drives are tricky to figure out. SSDs come in different form factors, with different connection interfaces, and with different types of flash memory. All these are important parameters that determine the speed of work, the affordability of drives, their reliability, and durability. And here in one of these important parameters – in flash memory – I propose to understand in detail.
Let’s look at SSD memory types, depending on their design and information storage technology. And what type of memory is best for SSD.
SSD memory types: 3D NAND, MLC, TLC, QLC, 3D XPoint: which one is better
If you want to buy an SSD and go to a marketplace on the Internet where solid-state drives are sold, you will see among the filters different types of memory MLC, TLC, the same types, and QLC with the addition of 3D NAND, V-NAND, 3D XPoint, etc. P. And also some type of memory will appear in the characteristics of the drive models. What does this all mean?
To store information in an SSD, flash memory is used – solid-state semiconductor non-volatile memory. This rewritable memory has such a feature that it can be read any number of times, however, it is possible to write data into the cells of such memory only a limited number of times. How limited the number of times data can be written to a memory location determines the type of flash memory. In addition to the wear resistance of the cells, the type of flash memory also determines the speed potential of the drive, its reliability, power consumption, and cost. The types of flash memory are different and have two division criteria – depending on the memory design (NOR and NAND) and depending on the information storage technology (SLC, MLC, TLC, QLC).
Flash memory types by design: NOR and NAND
There are NOR and NAND flash types depending on the design. Both appeared back in 1988-1989, NOR is the development of Intel, NAND is the development of Toshiba. They differ in the way of connecting cells into an array. NAND is faster and cheaper than NOR. NOR is used primarily in microprocessors and other devices for storing small amounts of operational data. Those. used as direct memory for microprocessors and other devices. The type of NAND flash memory is commonly used in flash drives, memory cards, and SSDs. NAND has an evolutionary continuation, so to speak, a successor – a type of flash memory 3D NAND that appeared in 2013.
3D NAND: the evolution of NAND
NAND Flash is a memory based on flat, single-layer structures, i.e. cells in a memory chip are arranged in one layer. As memory cells grow on a flat surface of NAND memory, placing them closer to each other more than a certain distance leads to a decrease in the reliability of the SSD. To go beyond this conditionality and be able to manufacture SSDs with large volumes, flash memory manufacturers had to come up with a solution to layered memory cells, i.e. stack cells in several layers, one above the other. That, in fact, this conditionality was the reason for the evolution of NAND into 3D NAND.
Samsung became the parent of 3D NAND, and it was Samsung who introduced the world to the world in 2013 with an improved design of NAND memory with a three-dimensional structure. But 3D NAND is the general name for the evolved NAND flash memory, and it is its technology that Samsung calls V-NAND – from Vertical NAND. 3D V-NAND received a vertical (hence Vertical) three-dimensional (hence 3D) structure of a memory microchip. That, accordingly, increased its area and made it possible to significantly increase the volume of stored data. But more than that: such a solution made it possible to further increase the reliability of data storage, increase the speed of memory and reduce the cost of its production. Samsung’s first 3D V-NAND had 24 storage layers. As Samsung’s 3D V-NAND technology developed, the number of layers increased: in 2014, memory with 32 layers appeared, in 2016 – with 64 layers,
Later, Micron, Toshiba, and others developed their own types of 3D NAND flash memory with a slightly different design. For example, Toshiba’s 3D NAND memory technology is called BiCS Flash. Other manufacturers of 3D NAND memory do not name their technology in any way, and, accordingly, for SSDs using their memory, 3D NAND is simply indicated in the specifications. And since today 3D NAND is produced by different manufacturers using different technologies, such memory can differ in durability, speed, data storage reliability, and cost.
What type of memory for SSD is better – NAND or 3D NAND – such a question, friends, could have stood a couple of years ago. But now, in 2021, 3D NAND has practically pushed NAND out of the market. But if you still have a choice – NAND or 3D NAND, take the latter. But if you choose between specific 3D NAND technologies, I would recommend Samsung’s V-NAND, the latest generations of this memory have good performance and durability. So far, only Samsung itself produces V-NAND-based SSDs. But with the drives of this company has its own nuances, Samsung has its own ideas about the types of memory MLC and TLC. And we will talk about this in detail at the end of the article.
We figured out that NAND or 3D NAND are all structural types of flash memory drives, but the information in NAND and 3D NAND can be stored using different technologies: SLC, MLC, TLC, QLC. For example, there are drives with NAND MLC and NAND TLC memory, and there are 3D NAND MLC, 3D NAND TLC, 3D NAND QLC.
Types of flash memory depending on the storage technology: SLC, MLC, TLC, QLC
Depending on the information storage technology, the types of flash memory are SLC, MLC, TLC, QLC. Basically, they differ in the number of bits of information that a memory cell stores. Each of these types of memory has certain characteristics. So:
- SLC is a type of flash memory that provides a single-level cell in which only 1 bit of information is stored. And this is the very first type of SSD flash memory. It is characterized by the qualities of good wear resistance, reliability, low power consumption, high performance. But because of the low data density in this memory, drives with a large capacity are very expensive. That is why SLC memory is practically ousted from the market today by a type of memory with a higher data density and, accordingly, more affordable at a price per GB.
- MLC is a type of flash memory with two-level cells, in which 2 bits of information are stored. It has optimal indicators of wear resistance, reliability, energy consumption and productivity. Costs less than SLC memory.
- TLC is a type of flash memory with three-level cells, in which 3 bits of information are stored. It has indicators of wear resistance, reliability, power consumption and performance worse than that of the MLC, but it is also cheaper than the MLC.
- QLC is a type of flash memory with four-level cells, in which 4 bits of information are stored. It has even worse durability and performance than the TLC, and is even cheaper than the TLC. This is a relatively new type of memory, designed to make SSDs with a large amount of mass available and finally send HDDs to the past.
Since SLC memory is practically not found in the corporate segment of the market, and QLC has not yet gained momentum and is at the stage of getting rid of childhood diseases, the main types of flash memory, depending on the information storage technology, which make sense to consider, are MLC and TLC. TLC memory is quite suitable for mass use: ordinary users do not perform large amounts of data rewriting, and the speed of their typical operations on a computer can be provided by drive caching technologies. MLC memory is of course preferable, but that’s in general. When choosing an SSD, you must also take into account other factors, we will consider them at the end of the article.
Here if you want to know about M.2 SATA Vs M.2 PCIe.
3D XPoint: an alternative to flash memory
And let’s consider, friends, another type of SSD memory – 3D XPoint, let’s consider, however, for the sake of idle interest. This is the newest type of solid-state storage memory, there are not many of them on the market, but you can already come across a filter of this type of memory on the Internet marketplaces. 3D XPoint is not flash memory, it is a completely new type of non-volatile cell memory with a mechanism for recording information into cells based on changes in the resistance of the material. 3D XPoint is potentially faster than flash memory and more durable. 3D XPoint was created jointly by Intel and Micron, Micron-based drives are not widely used, but Intel Optane drives based on 3D XPoint are present on the market. Intel Optane is a PCI-E SSD over M.2 and U.2 connectors. Some of the models have PCI-E 4. 0 x4 colossal data processing speeds: read – up to 7200 Mb / s, write – 6200 Mb / s. But Intel Optane with the PCI-E 3.0 x4 interface have very ordinary abilities – they process data no more than 2500 MB / s.
Whereas the Samsung 970 EVO Plus 1 TB (!) Based on TLC 3D V-NAND flash memory with the same PCI-E 3.0 x4 interface can read data at a maximum speed of up to 3500 Mb / s, and write up to 3300 Mb / s. With. And the Samsung 970 EVO Plus model with a base volume of 250 GB (although its data recording speed is lower – 2300 MB/s).
So, friends, we are looking at 3D XPoint so far only as a monster that is coming on the heels of flash memory manufacturers, which, perhaps, in the future will slowly approach their price niches and make SSD drives based on flash memory even more affordable. …
How to choose the type of memory for an SSD
Well, let’s summarize: what type of memory is better for SSD? For home use, the best memory options are 3D NAND MLC and 3D NAND TLC. Choosing between the two, you can give preference to 3D NAND MLC. But you need to consider factors such as:
- First, SSD manufacturers can equip their devices with different caching technologies to improve storage performance. Indeed, some TLC drives may be faster than MLC drives;
- Secondly, if you buy an SSD with a SATA interface, then due to the bandwidth limitations of the interface itself, you simply will not notice the difference in data processing speed between MLC and TLC. And also the power consumption and endurance performance of TLC drives can be better than MLC drives. The novelty of the drive will play a huge role here: newer generations of TLC drives may be better than older generations of MLC drives.
- Thirdly, do not forget that the primary type of 3D NAND memory, manufactured by different manufacturers, can somehow affect the quality of the drive as a final product.
How to find out what type of memory an SSD has before buying
Friends, even if the types of SSD memory are indicated in detail on the marketplace, you still need to clarify the information. On trading floors, there can be elementary errors and inaccuracies. In theory, I should advise you to look at the official website of the drive manufacturer. And it is from the primary source of the characteristics of the drive to learn everything about the types of memory. But I will not do that. Why? First, super budget drives may not have a spec sheet on a manufacturer’s website, just as there may not be a manufacturer’s website. Secondly, friends, alas, many manufacturers do not tell the truth about the characteristics of storage drives: they provide information incompletely, only in a favorable light for themselves. And sometimes they just stupidly lie. And this applies not only to creepy little-known manufacturers but also to well-known companies.
For example, Kingston only specifies the type of 3D NAND memory. And does not indicate the type of MLC, TLC, or QLC.
In such cases, I propose to go to the site and look at the characteristics of the drives in its database. According to the same Kingston drive, found information that its memory type was TLC. Well, in fact, this is what Kingston is embarrassed about, hiding this detail on its website. And by the way, what else is the benchmark websites base good for? The fact that in some cases indicates the TBW data rewriting resource. Many SSD manufacturers are silent about this important parameter, although, in theory, they should have covered this kind of information.
But, friends, we get a lot more marketing tin from the manufacturer if we go to the specifications page of Samsung Evo series drives. For example, here is the Samsung 970 Evo Plus SSD specs page on the Samsung website. And here it is written in black and white that the memory type of the V-NAND 3-bit MLC drive.
Above we said that MLC is a type of memory with the ability to write 2 bits of information into cells. If 3 bits of information are written to the cells, then this is a TLC memory type. Actually, this is what is given in the characteristics on the NIKS website with a note in the form of a reference to the Samsung specifications, in which the company claims that the type of memory in the device is some kind of 3-bit MLC.
Friends, at least officially there is no such type of memory as 3-bit MLC. As there is no 2-bit SLC or 4-bit TLC. Samsung Evo drives have a TLC memory type and nothing else. And this is stated by the AIDA64 program, which, among the diagnostic data, shows the types of SSD memory.
Samsung’s attempt to wishful thinking is not good, but friends, I would not want to belittle the advantages of Samsung Evo, these are really good drives for their money, and this, by the way, is a real example of a good TLC memory.
If you want to know exactly what types of memory it has before buying an SSD, see the specifications on the benchmark websites. Well, if it is possible to diagnose the drive, you can look at the memory type in the AIDA64 program.