Why an SSD moves data behind the scenes
Flash memory cells tolerate a limited number of program-and-erase cycles. An SSD controller spreads writes across available storage through wear levelling, rather than repeatedly wearing out the same physical area. The address the operating system uses can therefore stay unchanged while the data's physical location moves.
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Logical addresses hide physical management
An operating system requests data using logical storage addresses. Inside an SSD, a controller maps those addresses to physical flash locations.
Flash has constraints: data is written in pages, erased in larger blocks and gradually worn by program-and-erase cycles. Repeatedly updating one physical area would concentrate that wear.
Wear levelling distributes use across the available flash. The controller can place updated data elsewhere and change its internal mapping while presenting the same logical address to the computer.
- Logical addresses provide a stable interface.
- Physical placement can change beneath that interface.
- Background management prepares space for future writes.
Moving and reorganising data can produce additional internal writes beyond the host's original request. This helps explain why an SSD is an actively managed storage system rather than a passive array of fixed locations.