In July of this year, Toshiba and Western Digital took the lead in announcing 96-layer stacked 3D QLC flash technology, which can achieve 1.33Tb on a single chip, and can achieve an amazing capacity of 2.66TB in a single package. It is a 2.5-inch SSD with a capacity of 10TB. Not a very difficult thing.
Subsequently, Intel and Samsung also demonstrated the same 96-layer stacked 3D QLC flash memory technology, and the storage density is far better than the original TLC flash memory products. At one time, QLC has the potential to spread the popularity of large-capacity SSDs. It seems to be within reach.
However, consumers do not buy QLC flash memory. Many people question their reliability and performance. MLC and TLC are too backward and embarrassing.
In view of this, we will talk to readers about the practicality of QLC and other things related to SSDs.
First, QLC reliability is really poor, but the future is still its
SLC can only store 1 bit of data per Cell, and the voltage is only 0, 1 and 2 changes. Due to the simple structure, the rewritable life is up to 100,000 times, and the single Cell read and write speed is also 35/25MB/s.
MLC can store 2 bits of data per Cell. It can double the capacity of SLC under the same area, but there are four voltage changes of 00, 01, 10, and 11. It requires more complicated voltage control than SLC. It also grows longer, so the reliability is only 1/10 of that of SLC. The current MLC product rewritable test is usually between 3000~10000 times, and the read/write speed is also reduced to 1/3 of SLC flash memory.
TLC can store 3bits of data per Cell. Under the same area, the capacity can be increased by 50% compared with MLC, but there are 8 kinds of voltage changes, and the reliability is further reduced, generally between 300 and 1000 times. The single Cell reading speed is still 10MB. /s, and the write speed is greatly reduced, less than 1/10 for SLC, only 1.5MB/s.
QLC can store 4bits per Cell. Compared with TLC, the storage density is increased by 33%, but there are 16 kinds of voltage changes, resulting in rewritable life of only 100~150 times. The read and write speed of single Cell is currently not available. The manufacturer's public information is expected to be further reduced compared to TLC.
Due to the superior reliability of SLC flash memory and the read/write speed of other flash memory chips, it is usually used as a cache for MLC and TLC SSD. Currently, SSD products on the market generally integrate 8~50GB SLC flash memory. As a cache. Usually our read and write operations are performed in the SLC cache, but when the write-once data exceeds the SLC cache capacity, the write performance of the SSD will be greatly reduced, especially in the case of TLC SSD. Under, the write speed is basically poor tens of MB / s (Flash chip eraser is slow and slower than write speed, so it takes a certain amount of time after the SLC cache is full to be fully released for next use).
Although major manufacturers are actively launching QLC particle SSD products, in fact, compared with TLC particles, it can only increase storage density by 1/3, but the life expectancy is reduced by nearly 10 times!
It seems that the capacity of QLC flash memory seems to be worth the loss compared to the lost lifetime. However, in addition to the rewritable number of flash granules, the life of the SSD is also very important, that is, the capacity of the SSD itself.
(Even if you do not use large-capacity data copy operations, the system disk also has a certain amount of writes when using the computer. Mainly from virtual memory, browser cache, windows system use and temporary files generated when running the application. Everyone uses a different environment. Generally speaking, the daily write volume is about 10~50GB. The usage period of the above table is calculated based on the 50GB writes per day. The service life of MLC is not mentioned, even with 128GB capacity, the theoretical write life can reach more than 20 years.
For TLC, when the SSD capacity reaches 1TB, the write life is far more than the 128GB MLC.
But QLC is not that simple. With only 100 rewritable lifetimes, 128GB SSDs made with QLC particles can only write up to 13TB, and heavy players are scrapped in less than a year. When the SSD capacity is increased to 1TB, the write capacity can reach 102TB, and it can last for 5-6 years under heavy use. And so on, the write life of 10TB QLC SSD is enough for normal players to use 56 years. As for 100TB QLC SSD.......
In general, QLC particles are not suitable for small-capacity SSD products. But when the SSD capacity reaches 2TB or more, you don't have to care too much about whether he is using TLC or QLC. Just use it.
Due to cost and capacity advantages, QLC particles will be used in large quantities in future civilian-grade high-capacity SSD products.
Second, develop normal use habits, make SSD longer and faster
1, SSD partition 4K alignment BIOS open AHCI option
SSD 4K alignment and the impact of the ACHI option on the SSD performance in the BIOS, I believe most players have to understand, the following figure is the speed difference in 2 cases.
When there is no AHCI aligned with 4K, in the AS SSD Benchmark software, the red characters of pciide-BAD and 31K-BAD will appear. The performance at this time is terrible, and only the performance of SDD 1/3 is not enough.
Currently, the new motherboard basically opens the AHCI option by default. So after the SSD arrives, you only need to pay attention to 4K in the partition.
2, to ensure that the SSD has at least 20% of the available capacity
There is a friend, his 120G solid state drive (the actual available capacity is 112GB), the available space is only less than 5GB, and the C drive D is red. This is a great hazard to the hard drive, not only Life, even the speed will be greatly reduced.
We know that flash granules have a P/E erasure limit, so the current SSD has balanced erase and write technology The data copied to the SSD will not be placed together like a mechanical hard disk. When a block is currently written to the data, it will be deleted immediately. When it is written again, the master will store the data in other areas to keep it. The number of writes per block is at a balanced level, so that a block is not repeatedly erased and discarded in advance.
From the previous we know that when used daily, 10~50GB of temporary file data will be written to the SSD every day. If the entire SSD only has 5GB of free space, and at least 10GB of data is written every day, TLC flash memory 300 times of rewritable life will soon be exhausted, so the solid state drive must retain at least 20% of the available space.
The above said the impact on the life of the solid state drive, let's talk about the impact of insufficient space on speed.
(Because there is not enough time for testing, the test data of a foreign media has been introduced) The above is the change of the read/write speed when the SSD capacity is used 50~100%. When the available space is 50%, the 㝍 speed is about 10 times faster than the available space. Why is the same SSD full? The degree of data is different, will there be such a big gap in performance?
The data deletion in the flash granule is not in a single byte but in a fixed block. The block size is between 256K and 20MB. Since the flash block data cannot be directly overwritten, So all SSDs have a problem with write magnification..
When 4KB of data is to be written to the flash block, if the entire block is just empty, the 4K data is directly written, and the write magnification is 1.
When 4KB of data is to be written to the flash block, if the 64KB block already stores 48K of data, then I am sorry, the original 48K data needs to be copied to the memory first, and then the master wipes all the data of the flash block. Except, the 4K data to be written will be written to the flash memory together with the original 48K data. In fact, a total of 52KB of data is written, and the write magnification at this time is 52/4=13.
The more free space available in an SSD, the lower the chance of this happening. When there is little space available in the SSD, the write magnification will increase, and the read and write speed of the SSD will drop dramatically.
In fact, SSD vendors have also considered the above situation, usually will reserve some extra space for SSD. For example, 240GB SSD will generally have 16GB of redundant space, 480GB SSD will generally have 32GB of redundant space, but this space can play The role is very limited.
In order to keep the SSD running smoothly, in order to make the SSD last longer, be sure to reserve at least 20% of the available space for the SSD.
Smartphone flash memory is also used for MLC and TLC particles, so the above conclusions apply equally to smartphones. When your smartphone is getting slower and slower, check if the available storage space is sufficient.
