Retired-Page Utilization in Write-Once Memory - A Coding Perspective
In write-once memory (e.g., flash), a cell's level can only be raised, and erasure is only in bulk. The total number of erasures (endurance) is limited, and drops sharply with technology shrinkage and with cell-capacity increase. The normalized write capacity (ratio of total amount of data that can be written to storage capacity) drops similarly. Various coding schemes enable overwrites at the expense of storage capacity. With all of them, whenever desired data cannot be written to its current page, the page is \"Retired\" for subsequent erasure.