flashNAND

flashNAND is a type of non-volatile flash memory that stores data using floating-gate transistors. Unlike NOR flash, which provides direct access to individual bytes, NAND flash organizes data into blocks and pages. This block-based structure allows for higher density and lower cost per bit, making it suitable for mass storage applications.

Data is read and written in pages, typically ranging from 2KB to 16KB. Erasing operations, however, must be performed on entire blocks, which are much larger than pages. This erase-block constraint is a fundamental characteristic of flashNAND and necessitates the use of a flash translation layer (FTL) to manage data placement and wear leveling.

The FTL acts as an intermediary between the host system and the raw flash memory. It maps logical block addresses from the host to physical page addresses on the NAND chip. To address the erase-block limitation and ensure even wear on the memory cells, the FTL employs techniques like wear leveling, which distributes write operations across all blocks. It also handles bad block management, identifying and marking blocks that have become unreliable.

flashNAND is widely used in solid-state drives (SSDs), USB flash drives, memory cards, and embedded systems where high-capacity, cost-effective storage is required. Its performance, particularly in terms of read and write speeds, has significantly improved over generations, making it a dominant force in modern storage solutions.