The editor said: This time let's talk about what changes have taken place in SSDs over the past few decades.
Flash memory particles "super-evolved": from 2D NAND to 3D NAND
When it comes to SSDs, there is a topic that cannot be bypassed, that is, players often talk about "particles". Veteran players should know that SSDs are often discussed chips including master, flash, and DRAM, and the discussion about particles is the highest one. The flash memory particles that are widely discussed at present actually belong to NAND flash memory, which has been widely used in our daily personal computers since 2009 appeared on solid-state drives.
The two black chips on the right are flash memory particles
One of the characteristics of the working mode of NAND flash memory is that if we want to write data to the flash memory that has already written data, we need to erase its data before it can be rewritten. As the number of erases and writes increases, THE NAND flash memory will be worn, which is why the life of SSDs is described as "erase and write times".
Early NAND flash memory was laid on a flat surface, called "2D NAND". To take a less appropriate example, just like we design parking spaces in the parking lot, no matter how exquisite the route is in the case of fixed ground area, the parking lot can accommodate a limited number of parking spaces, in order to cope with the increasing demand for parking (data storage), it has to do multi-storey parking lots, one floor is not enough, then do two or even three floors. In the 2D NAND era, manufacturers in order to make the best use of the limited area only continue to use new processes, but with crosstalk and other problems leading to flash memory particles can no longer rely solely on process progress to bring improvement, Toshiba and Samsung began to bet on 3D NAND (Samsung called it V-NAND).
3D NAND helps reduce costs
NAND flash memory is also the same reason, "2D NAND" capacity is limited, then do "3D NAND", the current magnesium has achieved 176 layers of NAND mass production, flash density and cost compression reached an unprecedented height, in the near future, 192 layers of NAND is also about to be mass production, when higher capacity, lower cost of solid-state drives are expected to be born.
Diversification of commercial flash types The types of flash memory that have grown amid controversy: from SLC to QLC
According to the working principle of SSD, its data is stored in the semiconductor unit, of which there are four main types that have been widely commercialized, namely SLC, MLC, TLC, QLC, of which SLC belongs to 1bit/cell, MLC belongs to 2bit/cell, TLC belongs to 3bit/cell, and QLC belongs to 4bit/cell. This value means that the data of each storage unit, such as SLC has only one bit of data per unit, and the more data bits in a single storage unit, the higher the accuracy of the master control.
Image source wikipedia
Therefore, the durability of SLC particles P/E (life), speed and cost are the highest in each type, and these parameters decrease with the increase of data in the cell, from MLC to TCL to QLC, and even 5bit/cell PLC will become commercial products in the future.
Through data comparison, you can more intuitively know the parameter differences of different types of NAND flash memory, the number of erases and writes of SLC NAND flash memory is more than 10000 times, the number of erase and write times of MLC NAND flash memory is between 3000-10000, the number of erase and write times of TLC flash memory is between 1000-3000, and the number of erase and write times of QLC NAND flash memory is within 1000 times.
In the current application scenario of solid-state drives, the use of pure SLC NAND flash memory of the solid state drive is basically for military or commercial use, and MLC is mostly based on high-end consumer products and commercial products, to meet our daily use needs of solid state drives, TLC NAND is enough, as for the QLC NAND flash of the solid state drive, the advantage is that the capacity is large enough, a single complete erase cycle is extended, the short board of life can also be partially compensated.
QLC granules take SSD capacity to another level
Take Samsung, which has a wide range of product types, as an example, his SSD covers these four flash memory types, each representing the Samsung 970 Pro with MLC 3D NAND, the Samsung 980/Samsung 860 EVO with TLC 3D NAND, and the Samsung 860 QVO with QLC 3D NAND.
Consumer-grade MLC SSDs have been sharply reduced to the "hard to flat" in the hearts of consumers, the picture source unsplash
When talking about flash memory types, players often "have difficulty" in consumer MLC flash products gradually turn to commercial, TLC flash and QLC flash began to become the mainstream of consumer level. It's true that this process has long been controversial, but it's undeniable that consumers can now buy larger, higher-performance SSD products for less money.
The main control chip has been upgraded: from the improvement of technology, the reading and writing speed has increased by dozens of times
Manufacturers can safely use TLC and QLC flash memory with lower theoretical life, mainly because the main control chip is becoming more and more powerful, and most of the SSD parameters we can see are inseparable from the master control, such as read and write speed, interface protocol, TRIM support, wear balance and garbage collection mechanism. From the SATA SSD with a high cost and a read speed of only 1 or 200MB/s in the past to the PCIe 4.0 SSD with a sequential read speed of more than 7000MB/s today, these intuitive parameters are inseparable from the continuous upgrading of the SSD master.
Source Lianyun official website
The master control of the SSD belongs to the "central brain" of the entire product, on the one hand, he has to communicate with the host through the external interface, receive and process the host's orders, on the other hand, he also has to manage the "less intelligent" flash memory, store data more quickly and properly, and take into account the life of the flash memory chip.
The SSD parameters we see are more like the "forks" of the main control parameters, the source of the picture
The concept of jerky abstraction is not easy to understand, more important to our ordinary consumers, from the birth of the SSD master controller so far, this chip has been rapid development, and support more to ensure data integrity and data security, monitor the health of hard disks, extend the life of flash particles, such as TRIM, S.M.A.R.T technology, bad block management, LDPC error correction, power protection and so on.
It is precisely because of the increasingly powerful master control that the TLC SSD, which has long been despised by consumers, has been able to "turn over" into the mainstream of the current consumer-grade SSD, and even spawned a number of high-end SSDs that have been recognized by users. The main control chip is so important, the research and development ability of the main control has become the hard power of the storage product development manufacturer.
Elpis is currently Samsung's flagship
At present, both self-developed master control also output consumer products, naturally has a strong supply chain of Samsung, its self-developed master control is only applied to its own products, currently applied to the Samsung 980 Pro Elpis master control, with V-NAND 3-bit MLC flash memory (that is, TLC) and 2GB DDR4 SDRAM, can achieve up to 7000MB/s sequential read speed and 5100MB/s sequential write speed.
In addition, mainstream first- and second-tier manufacturers such as Mapai, Lianyun, Qunlian, and Huirong also provide a wealth of main control products for third-party manufacturers to purchase for different positioning, and some manufacturers also provide one-stop integration solutions. The SSD products on the market can show a hundred flowers, and it is inseparable from the efforts of a number of master control solution providers.
Single-disk capacity leaps forward: from 32GB in 2007 to 8TB in 2020
There are so many technical concepts laid out in front of us, but we have to admit that for our ordinary consumers, the first thing that comes to mind when talking about the hard disk is the capacity, after all, as the most intuitive performance of how much data we store, the change of capacity is the comprehensive embodiment of the flash memory, master control and other factors mentioned above.
Back to the title, the world's first commercial SSD was launched by SanDisk in 1991, its capacity is only 20MB, and in 2018, the ExaDrive DC100 SSD launched by Nimbus Data has the amazing capacity as the name suggests, this 100 does not represent 100GB, but 100TB! In the past 27 years, the capacity of commercial-grade SSDs has increased by a million times, and if commercial products are too far away from our consumer end, it is better to return to consumer-grade products.
How much "data" can this hard disk put, picture source network
From the 2.5-inch 32GB SSD released by SanDisk in 2007, to 2020, consumers have been able to buy 8TB capacity SSDs, and it is no wonder that more and more consumers perceive that the capacity of SSDs has greatly surpassed the momentum of mechanical hard drives. Although the large-capacity SSDs we can buy at present are most likely "unpopular" QLC flash products, the advantages of the SSD's own random read and write performance are incomparable to the mechanical hard disks, and they are also the magic weapons to help the rapid popularization of large-capacity SSDs in the foreseeable future.
With a QLC particle capacity of up to 1TB, the service life is no longer the most important concern
As for the "life problem" that players are worried about, we can compare the Samsung 840 EVO that used TLC flash memory for the first time with the Samsung 860 QVO that used QLC flash memory for the first time, the former's 1TB version of the official durability value is 72TBW, and the latter's 1TB version of the official durability value has risen to 360TBW, although both are far behind the Samsung 870 EVO 1TB version of the 600TBW, but this also shows that with today's master control technology and flash memory process, The life of the QLC SSD is not as bad as imagined. It is worth mentioning again that the 8TB capacity version of the Samsung 870 QVO has a durability value of up to 2880TBW, and it can be used for nearly 8 years according to the daily writing of 1TB of data.
Unsatisfactory write speed is the main reason why QLC "dissuades" consumers
What we are really worried about is the slow external performance decay of QLC solid-state drives, taking the Samsung 860 QVO we have evaluated as an example, its 1TB version of the slow external write speed is only 80MB/s, which is already lower than the level of mechanical hard disks, even if it is a 4TB version, its slow external write speed is only 160MB/s, so the current positioning of QLC solid-state drives is still a storage disk, not suitable for frequent reading and writing of the working environment.
Summary: SSDs have long been integrated into life
As SSD products continue to improve and mature, we have not heard for a long time whether it will replace other types of hard disk debate, instead, we see more and more consumers discussing which SSD is suitable for what application scenarios, which is the proof that SSDs are truly integrated into our lives.
At present, the consumer-grade SSD market has not yet had a real monopoly-level giant born, and as consumers, we can still enjoy the dividend of "a hundred flowers blooming". However, with the upgrade of the PCIe Gen5 interface and the emergence of new flash memory, perhaps a new round of updates is coming, so let's wait and see.