UBIFS
File system permissions | Unix permissions |
---|---|
Transparent compression | Yes |
Other | |
Supported operating systems | Linux |
UBIFS (UBI File System, more fully Unsorted Block Image File System) is a flash file system for unmanaged flash memory devices.[1] UBIFS works on top of an
Two major differences between UBIFS and JFFS2 are that UBIFS supports write caching,[5] and UBIFS errs on the pessimistic side of free space calculation.[6] UBIFS tends to perform better than JFFS2 for large
UBIFS stores indexes in flash whereas JFFS2 stores filesystem indexes in memory.[9] This directly impacts the scalability of JFFS2 as the tables must be rebuilt every time the volume is mounted. Also, the JFFS2 tables may consume enough system RAM that some images may be unusable.
UBI
UBI (Unsorted Block Images)
UBI's documentation explains that it is not a complete
UBI is in some ways analogous to a
gluebi
it's possible to emulate a MTD device, which can then be used to run other flash filesystems like JFFS2 and YAFFS, and using ubiblk
it's possible to emulate block devices, which can run common filesystems like Ext4.
Fastmap
UBI was augmented in Linux 3.7 with fastmap support.[11][12] Fastmap maintains an on-disk version of information previously created in memory by scanning the entire flash device. The code falls back to the previous mechanism of a full scan on failures and older UBI systems will simply ignore the fastmap information.
See also
References
- ^ Jonathan Corbet (2 April 2008). "UBIFS". LWN.net. Retrieved 18 December 2016.
- ^ "UBIFS – UBI File-System: Big red note". 22 January 2015. Retrieved 18 December 2016.
It does not work on top of block devices. UBIFS was designed to work on top of raw flash.
- ^ "UBIFS – UBI File-System: Overview". 22 January 2015. Retrieved 18 December 2016.
- ^ Artem Bityutskiy (27 March 2008). "UBIFS – new flash file system". Retrieved 18 December 2016.
- ^ "UBIFS – UBI File-System: Write-back support". 22 January 2015. Retrieved 18 December 2016.
- ^ "UBIFS FAQ and HOWTO: Why does df report too little free space?". 18 December 2015. Retrieved 18 December 2016.
- ^ "UBIFS – UBI File-System: Scalability". 22 January 2015. Retrieved 18 December 2016.
- ^ a b Bityutskiy, Artem; Hunter, Adrian (24 September 2008). "UBIFS File System" (PDF). p. 9.
- ^ Adrian Hunter (27 March 2008). "A Brief Introduction to the Design of UBIFS" (PDF).
- ^ "UBI – Unsorted Block Images". 22 January 2015. Retrieved 18 December 2016.
- ^ Thomas Petazzoni (3 October 2012). "UBI fastmap making its way to mainline". Archived from the original on 15 November 2012. Retrieved 18 December 2016.
- ^ Richard Weinberger (24 September 2012). "UBI: Fastmap request for inclusion (v18)". Retrieved 18 December 2016.
External links
- Home page
- University of Szeged: UBIFS Archived 28 September 2013 at the Wayback Machine
- UBIFS experiments on the XO Laptop (One Laptop per Child)
- UBIFS file system