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Refusal
This is a revised version of an article posted to Qiita in November 2019.
Introduction
To ensure the optimal lifespan of SSDs, it is necessary to mitigate the factors that consume the NAND flash memory mounted on the SSD, other than TBW(Total Bytes Written). However, since the impact of these factors greatly depend on the characteristics of the product, making it difficult to generalize whether larger factors are detrimental. Nevertheless, effective utilization of the product can prevent the increase of these factors and prolong the lifespan of the SSD.
Therefore, this article will continue from the previous article to introduce what kind of usage patterns will harm the SSD.
By avoiding the usage patterns outlined in this article, users can expect to maximize TBW and extend the life of their SSD.
Summary
- Operating environment plays a big role (temperature, vibration etc.)
- Don’t turn off the power!
- No unstable power supply!
Operating environment plays a big role (temperature, vibration etc.)
＜Points: Temperature is not the only factor should be aware of＞
In SSD operation, the operating ambient temperature, in addition to the temperature rise caused by heat generated by the SSD itself, should be considered.
The controllers of SSDs are susceptible to high temperatures, just like other semiconductor chips, while NAND flash memory should be operated at a low temperature, as its data retention capabilities deteriorate under high temperatures.
Additionally, temperature changes should be taken into account since NAND flash memory has a characteristic that increases the error rate when the difference between the temperature at which data is written and the temperature at which data is read increases1. Therefore, SSDs should be used at a constant temperature as much as possible without getting too hot.
Vibration is another crucial operating factor that should be considered.
While it is often said that SSDs are resistant to vibration since they have no moving parts, the connectors used to connect SSDs can still be a nuisance.
If there are concerns about connectors, products that do not use connectors, such as BGA-shaped products, may be viable candidates. If necessary, the strength of the solder joints should be increased through underfilling. However, if the SSD is for equipment used in a well-managed environment such as an office or home, these precautions may not be necessary. Otherwise, the operating environment described above should be taken into account.
Don’t turn off the power!
＜Point: Proper power-off procedures should be followed to prevent SSD wear and data loss.＞
When shutting down an SSD, it is important to follow the proper procedures specified for SATA or NVMe to prevent unnecessary wear on the device.
Disruptive shutdowns such as disconnecting the SSD power supply by directly dropping the breaker to which the host PC power supply is connected can lead to a reduction in TBW and data loss.
If the SSD is notified of a power-off in accordance with the proper procedures, it will adjust its internal state to be ready when the power is turned off. However, if the power is turned off improperly, the SSD will align its internal state the next time it is powered on, which may require reads and writes to the NAND flash memory. These processes can consume the life of the device and reduce TBW.
The time and impact of this process varies by product, with some SSDs frequently taking internal state consistency to minimize the impact of unexpected power loss. While this reduces the time required for the internal state alignment process, it also leads to reduced TBW due to the additional wear on the device.
Other products minimize the frequency of internal state matching to reduce wear on the device, but this can lead to longer alignment times and a higher risk of data loss in the event of an unexpected power loss.
No unstable power supply!
＜Points: Defects caused by the power supply are difficult to correct later on and must be addressed in advance.＞
Unstable power supply can lead to unstable operation of NAND flash memory.
The operation of memory cells in NAND flash memory requires a higher voltage than the interface voltage between the SSD controller and NAND flash memory (e.g., 1.2 V or 1.8 V). Fluctuations in supply voltage can significantly affect the operation of NAND flash memory.
Our SSDs feature a function that detects power supply voltage drops and minimizes unstable operation of NAND flash memory, especially during data writing. Nevertheless, this function is only capable of reducing the damage caused by unstable power supply.
In conclusion, a stable power supply is the most optimal way to use SSDs.
Conclusion
In two articles, we have described “unfriendly usage” of SSDs, which can significantly reduce their lifespan.
The following summarizes the most common “life-decreasing uses” of SSD:
- Use SSDs with insufficient capacity
- Randomly writing to a large LBA space
- Continuous reading of the same data
- Exposure to harsh operating environments, such as high temperatures, large temperature differences, and strong vibrations
- Turning off the power supply without following proper procedures
- Using an unstable power supply
By avoiding these usage patterns, the SSD’s lifespan can be maximized.
In our next article, we will provide a specific checklist for “How to Select an SSD”.
Reference
- Fukuda,“Akira Fukuda’s Storage Communication: Micron’s Ideas for the Future of Memory Systems (3): Putting SSDs in Cars (1/2),”July 6, 2016 (viewed June 13, 2022).
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The content of this article is information at the time of publication. Please note that the information is subject to change without notice.
