NAND FLASH MEMORY 101 WEAR LEVELING
NAND flash memory has become the preferred flash memory format for storing larger quantities of data on devices such as USB Flash drives, digital cameras and MP3 players. Higher density, lower cost, and faster write and erase times, and a longer re-write life expectancy make NAND flash memory especially well suited for consumer media applications in which large files of sequential data need to be loaded into storage quickly and replaced with new files frequently.
An important aspect of design with NAND flash memory is the software (sometimes called firmware) that controls and manages the flash memory itself. In particular NAND wear leveling is crucial for proper function and long life of the flash-based device. A unique and challenging aspect of managing NAND flash memory is the fact that it wears out over time. Without special handling in software, flash memory does not wear uniformly, meaning that some areas of the flash memory will wear out sooner than others. It is vital that the flash memory manager include an effective wear-leveling algorithm to ensure the maximum possible product lifespan.
Not all wear-leveling algorithms are created equal. A key aspect of a wear-leveling algorithm is its effectiveness (or ability at all) to wear-level data which is completely static in nature, known as static wear leveling. Many OEM products contain data which is stored in flash at manufacturing time, and is never changed. This static area effectively reduces the amount of flash memory available for reads and writes, concentrating the wear areas and thus shortening the lifespan of the flash. At their most basic, wear leveling algorithms use dynamic wear leveling, which directs system writes to areas of the flash that have been used least.
The ideal NAND wear leveling scenario is one where both static wear leveling and dynamic wear leveling are used together. The FlashFX Pro intelligent flash memory manager by Datalight does both. As flash densities increase, and the corresponding flash lifetimes decrease, capabilities such as this will become increasingly important in ensuring the maximum lifetime of OEM products. For more information on Datalight FlashFX Pro, visit www.datalight.com/products/flashfx