File systems for mobile phones or handheld devices
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This document discusses various file systems used for mobile phones and handheld devices with flash storage. It describes Linux flash file systems like JFFS, JFFS2, YAFFS, UBIFS and the newer F2FS. It also discusses TrueFFS flash management software and the flash transition layer. Finally, it mentions the file system used for iOS and proposes a distributed file system for improved mobile computing.
File systems for mobile phones or handheld devices
- 1. File Systems for Mobile Phones or Handheld Devices By Ram Kumar K R Ganesh Arkalgud
- 2. Introduction • Flash Storage • Linux Flash File Systems • Flash Transition Layer
- 3. Linux Flash File Systems • JFFS – Journaling Flash File System • JFFS2 – Journaling Flash File System 2 • YAFFS – Yet Another Flash File System • UBIFS – Unsorted Block Image File System • F2FS – Flash Friendly File System
- 4. TrueFFS • Patented flash management software • By M – Systems • Software layer between OS’ File System and Hardware. • Provides block device functionality and flash media management
- 6. JFFS2 • Log-structured open-source file system • NAND and OneNANDTM Flash memory devices • Developed and maintained within the Memory Technology Device (MTD) layer • Garbage collection • Wear leveling • Power loss recovery
- 8. YAFFS • Yet Another Flash File System • NAND model – chunks and blocks • Linux, RTOS and devices with no OS • YAFFS1 • YAFFS2
- 11. • Tree of objects of type YAFFS_OBJECT_TYPE_DIRECTORY. • not stored in NAND but are instead created on mounting • lost+found • Unlinked and deleted
- 12. UBIFS • For Raw – Flash Systems • Fix JFFS 2 Issues such as • Faster mount • Fast opening of big files • Faster write speed • Maps Physical Erase Blocks(PEB) to Logical Erase Blocks(LEB) • Disadvantages • Scales Linearly • Reads all block headers during initialization • Time for initialization increases with flash size
- 15. Flash Transition Layer • Makes flash appear as a disk drive for OS • Enables mounting FAT, ext and other file systems on to a flash drive.
- 17. F2FS • Assumes presence of Flash Transition Layer • Log – structured design • On disk layout - Block (4K in size) Segment (2MB in size) Section (consecutive segments) Zone (set of sections) Area (multiple sections) Volume (six areas)
- 19. Test Results of F2FS
- 20. iOS File System • Each app is an island • Public system interfaces
- 22. A Distributed File System for Mobile Computing • Efficient variable consistency replication • Intelligent file prefetching • Trade off between availability and consistency
- 23. References • www.yaffs.net • Software Profile: Journaling Flash File System, Version 2 (JFFS2) By Luca Boschetti,Micron Software Engineer • TrueFFS® 6.x Software Development Kit (SDK) Quick Reference Guide • iOS File System Programming Guide by Apple Inc. • UBIFS file system by Adrian Hunter and Artem Bityutskiy, Nokia Corporation • Understanding the Flash Translation Layer (FTL) Specification by intel corporation. • Flash Friendly File System overview by Leon Romanovsky • A Ph.D thesis on File System for Mobile computing, by Dr. Carl Downing Tait