Write amplification is an undesired phenomenon in SSDs when more writes to the NAND occurs than necessary. Due to most NAND having a limited number of write/erase cycles, high write amplification could significantly impact the lifespan of an SSD.
Write amplification could happen in a variety of ways, but the most common way it can occur is the way the SSD handles modifications to a specific block of data. Storage blocks are divided into pages, and pages within the SSD can’t be deleted individually. This means that whenever a few pages need to be altered, all the old data within the block needs to be erased and rewritten to include the modified data, wasting erase/write cycles in the process.