Yaffs was designed from the ground up for Flash memory. It is best with NAND Flash but can be used with NOR too. It has mechanisms for wear-levelling, and special attention has been paid to the safety of the system even under power-failure. It is works well with MLC Nand, as well as SLC; it is compatible with a wide range of Flash, including Toshiba/Sandisk MLC parts. See also the document Considerations in Using a Flash File System for a discussion of the importance of reliability.