Flash Endurance & SSD Wear Leveling Algorithms
Although SLC NAND Flash memory provides a high level of performance, it still has a finite lifespan. There are only so many times a program and erase cycle can occur before a failure takes place and data is put at risk. To ensure that SLC memory lasts for as long as possible, SSDs rely on wear leveling algorithms. These algorithms ensure that writes are evenly distributed throughout the SSD so that blocks do not wear out prematurely. To further explain SSD wear leveling algorithms here are the main concepts.
In a perfect world, when a host system provides a logical block address (LBA) for data it wants to read or write, the SSD controller would read or write the LBA to the same physical block address. In reality, this doesn’t happen for many different reasons, including:
- File system directories that are not updated after files are changed.
- Mismatches in data sizes between the host and block sizes of the SSD’s NAND.
- The process of reclaiming blocks that have been previously written.
These are just a few of the factors that lead to non-sequential writing. Without any intervention, this could cause the NAND to use the maximum allowable number of endurance cycles for certain cells, without using other cells at all.
Wear Leveling and Endurance Cycle Balancing
Wear leveling algorithms that are used in SSD controllers address the impacts of non-sequential writing to maximize the efficiency of the SSD. There is no single method of wear leveling that is used across all SSDs, as designers often use their own versions. Some algorithms store host data for LBAs to a place with the smallest amount of used endurance cycles. Others move static data to different physical locations in the NAND so that the cells that previously held static data can be used for their maximum number of endurance cycles. Typically, SSD wear leveling algorithms work as part of a multifaceted approach for managing SSD endurance.
Do you have questions about SSD wear leveling algorithms or maximizing the lifespan of your SLC Flash storage? Delkin provides rugged embedded storage for industrial use and is happy to discuss your needs. You can also check out our product specs to see how our industrial flash storage can provide maximum performance for your industrial application.
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