NAND Flash has the characteristics of limited erasure times and erasure before writing, resulting in limited service life. In order to prolong the expected service life of storage units, the consumption balancing algorithm is generally used to manage each storage unit. The SSD data is stored in NAND flash memory, which has no moving parts.
For SSDs, the process of reading data is a process of resolving the address, so the data reading is very fast.
The data writing process is more complicated and consists of two processes: the data is erased and then written.
Solid-state drives are much slower to write than data is to read. Because writing data to SSDs is a bit more complicated, the controllers of SSDs perform a process called wearing-leveling, which rearranges the data inside. Some of the data will be moved from one location to another. To accomplish this, the SSD controller keeps a list of the locations of the data being moved. After adopting the attrition equalization technique, the read and write times of flash chips tend to be consistent, and a small part of the frequent read and write are distributed to the whole storage medium. The local aging of the FLASH chip is alleviated and its service life is greatly extended.
Dynamic Wear Leveling and Static Wear Leveling. Dynamic loss equalization (hereinafter referred to as dynamic loss equalization and static loss equalization) is limited to dynamic data (frequently moved data or deleted and transformed data) and unused space. That is, if data is written to a block, it is not covered by dynamic load balancing (called static data). Static load balancing does not. It forces stored data to be moved to a block with fewer writes, which increases life and reliability to a greater extent.
Over time, however, SSDs have less and less unused storage space, and in many cases, they have to erase data from flash before writing to it, so performance deteriorates significantly. Moreover, while the goal of attrition balancing is to prevent data from being written to a space repeatedly, it ensures that attrition levels are roughly the same across storage areas, thus making SSDs longer.