Concerning the Linux UBI and UbiFs layer for NAND and NOR flash chips.
Ubifs is a flash file system which support raw flash devices like NOR and SLC/MLC NAND flash. It does not support flash cards, like compact flash, MMC, SD, etc. which typically have built-in controllers. Ubifs was introduce to Linux in version 2.6.27 circa 2008.
UbiFs is layer upon UBI or the Unsorted block image layer. In turn UBI is on top of an MTD (media technology driver) which is basically a Linux flash driver.
- The MTD is a combination of the flash chip and a CPU interface to that chip; the flash controller.
- UBI provides wear leveling and volume management.
- UbiFs implements the actual filesystem and is simplified, compared to JFFS2, as it doesn't have to deal with wear leveling*. UbiFs uses many data structures, such as wandering trees, a tree node cache, B-trees, Journals, etc.
UbiFs was originally named JFFS3. However, as the design and compatibilty completely diverged in it's development, the name was changed to UbiFs.
References,
- UbiFs documentation
- UbiFs Faq
- UBI documentation
- UBi FAQ
- Wikipedia
- JFFS3 design, an old document with an overview of data structures in UbiFs.
