Wear leveling

A fragment of a road surface, heavily rutted by car wheels following the same path.
Deep ruts from car wheels following the same path. Repetitive use of memory cells leads to a similar effect. Wear leveling attempts to distribute "traffic" more evenly.

Wear leveling (also written as wear levelling) is a technique for prolonging the service life of some kinds of erasable computer storage media, such as flash memory, which is used in solid-state drives (SSDs) and USB flash drives, and phase-change memory.

A view on stairs, where the central part deteriorated from people using mostly the middle section of each step.
Uneven wear on the central section of stairs, from pedestrians following a single path. Another everyday-life example of a similar issue.

The idea underpinning wear leveling is similar to changing position of car tires, avoiding repetitive load from being used on the same wheel. Wear leveling algorithms distribute writes more evenly across the entire device, so no block is used more often than others.

The term preemptive wear leveling (PWL) has been used by Western Digital to describe their preservation technique used on hard disk drives (HDDs) designed for storing audio and video data. However, HDDs generally are not wear-leveled devices in the context of this article.

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