Write Amplification
The ratio between physical bytes written by a storage system and logical bytes written by the application, often increased by compaction or copy-on-write behavior.
Storage Context
Write amplification is the ratio between physical bytes written by a storage stack and logical bytes requested by the application. LSM compaction, database page rewrites, RAID behavior, copy-on-write mechanisms, and SSD garbage collection can all add writes at different layers.
Measurement Boundary
Ratios from two systems are not comparable until the accounting boundary is defined. Whether transaction logs, replication, filesystem metadata, or device-internal writes are included can change the reported value substantially.