SSDs are already the absolute standard for installation or purchase. With the development of SSD technology and products, how to pick a satisfactory SSD requires extra attention.
NAND flash memory technology continues to grow, from a single cell storing 1 bit (bit) SLC, to a single Cell storage 2 bit MLC, to the current mainstream Single Cell Storage 3 bit TLC, and soon to be popular single Cell storage 4 bit QLC With every technological innovation, the cost of flash memory has decreased exponentially, and the user is getting cheaper products.
And whether it's an SSD for personal computers or an eMMC/UFS for mobile phones, capacity will continue to double over the next few years, and purchase costs will become lower and lower.
Global NAND Flash Storage Density Trends (Source: China Flash Memory Market)
The SSD brand on the market is dazzling, so that the average consumer can't start. Here we use the data that the average user can capture, to snoop on the quality of an SSD, and let ordinary users choose the right one based on these surface data. Your own SSD.
JD.com has more than 8,000 products for SSD category selection
First, the impact of the number of flash memory particles on SSD quality
As we mentioned before, NAND flash memory technology has evolved from SLC to MLC and then to TLC. Currently, the main providers include Samsung, Hynix, Toshiba, Micron, Intel and SanDisk (acquired by Western Digital), and TLC is the absolute main force ( 3D NAND), and a small number of MLCs.
Each flash memory vendor has its own strategic layout. For example, Samsung’s flash memory is superior in performance, becoming the main and preferred choice for high-performance mobile phones (Huawei phones had been lying on the gun due to Samsung UFS supply problems). Intel’s flash memory is in mobile phones. The inside is hard to find, because a large number of CPUs are used in the server area and are known for stability and capacity, not performance.
The flash memory we see in non-original brand SSDs on the current market, Samsung and Hynix are the least used. The mainstream is mostly Toshiba/SanDisk and Intel/Micron.
Any SSD requires two parts of cooperation for stable operation, namely master + flash memory. The more the master can support a flash type, it can create a richer product, naturally more valuable. This is the basic business logic, but the current Although many control plants claim to support all the original flash memory on the market, the support for Korean flash memory is generally the same.
For example, Intel introduced 3D NAND in 2016, codenamed L06B, B0KB, where L06B is an MLC particle, uses ONFI 4.0 standard, each Die has a capacity of 32GB, a page size of 16KB, uses a 4-layer design, and has a flash memory life of 3000 P/. E (program erase cycle).
B0KB is a TLC particle. In fact, the same chip is used. Users can choose to adopt the MLC mode and TLC mode according to their needs. The capacity of a single Die is 48GB, but its lifetime is only 1500 P/E. Therefore, a higher LDPC ECC error correction standard is required. .
Intel 3D NAND architecture
A plurality of Die stacks are packaged as flash granules, MLC flash capacity is selectable from 32GB to 512GB (16-layer stacking), and TLC flash memory is available from 48GB to 768GB.
By means of a multiple die package, the capacity of a single flash memory particle can be made bigger and bigger, and there is a very basic logic that these particles are used in SSDs. That is, the higher quality Die, the more layers can be packaged, the capacity The larger the number of particles used by an SSD, the lower the chance of problems.
and so, When selecting SSDs, the smaller the particles and the greater the capacity, the higher the quality of the SSD.
The 120GB SSD recently seen on a dismantling site uses 8 TSOP encapsulated particles
Entry-level 120GB, 240GB solid-state drives, if TLC is not popular two or three years ago, may use multiple particles, but in the current TLC has become mainstream, users need to first choose Weigh the volume.
A recent 640GB SSD seen on a dismantling site uses a single BGA package particle
This should be the first to mention Intel TLC single can achieve a maximum capacity of 768GB, one can create a 640GB capacity SSD.
Second, the impact of OP reserved space on quality
OP reserved space, English name Over-Provisioning, refers to the SSD internal controlled by the main control chip, the user inoperable hidden space, used to control the operation of various optimization mechanisms, such as GC garbage collection, wear and balance and so on.
In layman's terms, The more OP space reserved for SSDs, the better the performance of GC recovery, wear leveling, etc., so as to improve and maintain the SSD's long-lasting high-speed, will not fall off, and naturally the more stable, the lower the rework rate and the longer life expectancy.
OP share of different usage capacity (from Kingston's official website)
In the MLC era, 128/256/512GB SSD capacity is more common. After entering the TLC era, 120G/240/480GB is more common. Intel SSD has 360/800GB in the server market, and Micron is more targeted at consumer applications. It is like to launch this wonderful volume of 275/525GB.
Can be extrapolated 360GB SSD If the original capacity of flash memory is 512GB, the reserved space ratio of the OP is as high as 42%. If the 275GB SSD is used with 192GB+96GB (B0KB produced by Intel Corporation), the OP value is 4.7%.
It can be seen that when the original factory is producing SSDs, it will set different OP values according to different markets to satisfy the market. For non-original brands, if TLC products, it is inevitable that the larger the OP value, the better.
Assembly of mechanical and commercial commercial 320G as the main hard disk to reduce the repair rate
It can be observed, Domestic large-scale assembly and electromechanical traders often use 320GB, 160GB of this special capacity, because this kind of product has a larger OP reserve. If it is 192GB open card is 160GB, OP value is 20%, by reducing the repair rate, Can reduce the round trip freight that it brings to repair.
Intel's S3520 Series for Servers
Intel S3520 uses MLC particles. If the entry-level 150GB capacity is made of 256GB particles, the reserved OP value reaches 70%! With a large number of OP values reserved, it can be guaranteed to run stably on the server. This also confirms the former Mentioned the corporate strategy of Intel Flash - priority to meet the needs of the server.
Third, don't be misled by SSD speed
The speed of the SSD depends on two levels, namely the way the master operates and the NAND flash used.
In terms of flash memory speed, Samsung has always been a Bug-like existence, and it is indeed unmatched in the same level of flash memory. At the main control level, different solutions will bring different SSD performances.
In the current TLC era, the main control given by the cheap solution is: Part of the TLC simulation SLC mode, the first part of the SLC as a porter, data written to the SLC, the highest efficiency; SLC written, the master personally go on as a porter, this time to reflect the true speed of the TLC.
As mentioned earlier, TLC is a cell that stores 3 bits, SLC is a cell that stores 1 bit, so TLC simulates the SLC mode and it can only simulate up to 1/3 of the capacity of the whole disk.
In order to meet the needs of different users, the main control companies also gave another solution, namely While TLC simulates SLC, add a DDR cache particle to allow cached particles to assist in handling data. Generally, 1GB flash memory handles the matching relationship of 1MB cache.
Test without cache 480G SLC mode (40G write)
Without buffering 480G fills over 1/3 of the above test (40G write)
500G filled with 1/3 full test above buffer (40G write)
This tool, called HD Tune Pro, allows users to actually test the true performance of the SSD and is not easily misled by the brand factory and the media.
The reason why there is no test read after the fill is because the reading of the SSD is basically the same. Generally, when we use SSDs, such as playing games, we basically read operations.
Today, there are still some people who mislead users to say that mechanical hard drives are better than solid state drives, and some people say that SSD performance is not as good as that of U-disks. It is really laughable.
Through the comparison of the above three figures, we can draw the following conclusions:
1, Regardless of whether it is a DDR scheme or a DDR scheme, the writing of the analog SLC segment is similar in terms of write comparison.
2, When the SLC simulation capacity is filled, the writing speed will change. The average speed of the solution with DDR is more than double the average speed without DDR.
3, Whether with DDR or without DDR, there will be a case where the minimum speed is lower than 10MB/s. This is because the master control determines the garbage collection function when carrying data. When looking at the writing of an SSD, The best assessment parameter is the average writing speed, and the highest and lowest values are for reference only.
If you need a lot of copy inhalers every day, choose the solution with DDR or Samsung's SSD will be the best choice.
Fourth, domestic flash memory is a long way to go
Finally, let's take a look at the trend and progress of domestic flash memory.
Yangtze River Storage recently announced that 32-layer stacked 64Gb 3D flash memory will reach mass production in 2018, and that 64-layer stacked 128Gb 3D flash memory will enter the stage of large-scale R&D in 2019.
Single Die 64Gb is also 8GB capacity, and we talked about Intel's previous generation of code-named B0KB TLC single Die 32GB, the current production of code-named B17 TLC single Die 64GB.
Thus, Even if the yield of domestic flash memory is the same as that of international manufacturers, the cost difference will reach 8 times. If Moore's Law continues to be effective in flash memory, the cost of domestic flash memory will still take a long time to achieve market competition.
At present, the trade war between China and the United States is continuing. In the face of such a controlled situation, we can only sincerely wish domestic flash memory to realize technological innovation and mass production at an early date, so that we can also use the SSD products of the Chinese core as soon as possible.
NAND technology continues to develop, and still follow Moore's Law, you can boldly predict that when the QLC era is officially coming, it will be possible for SSD to completely replace HDD.
In the choice of SSD, we need to master certain basic knowledge and follow the basic purchasing logic to avoid falling into other people's flicker traps.
