File System for the year of 2011 – ext4 in Android 2.3

21 Feb

Android 2.3 (code named Gingerbread) first showed up in the Google Nexus S phones.  One of the key changes is the new file system, ext4 (fourth extended file system), versus YAFFS (Yet Another Flash File System) that are in Android 2.2 (Froyo) phones currently in the market.

ext4 comes out from a 3-year development prior to Google’s announcement of Android 2.3 inclusion in December of 2010.  It can support volumes with sizes up to 1EB (exabytes) and files up to 16 TB (terabytes).  It uses extents, contiguous physical memory blocks, to improve the large file performance and reduce fragmentation from the block mapping scheme of ext2/3.  YAFFS is single threaded.and would have become a bottleneck of performance in dual-core systems.  Ext4 changes that and enables further optimization on dual-core phones that will come out in 2011.  All these improvements will come in handy when you start using the 10+MP cameras and 720p video recording features that come with the smart phones in the near future.

Another development of file system is Btrfs as part of MeeGo strongly supported by the US semiconductor giant – Intel Corporation.  Each of the two latest file systems has its advantages and disadvantages.  Btrfs is still under development and that’s the key reason it wasn’t selected as part of the Android 2.3.  ext4 beats it in timing and system stability requirements.

File systems for mobile devices got their attention because of the limited life cycle of the NAND Flash devices.  Wear Leveling has been the key objective of the file systems like YAFFS, JFFS2 and Samsung’s RFS.  However, all these earlier file systems are lagging in their performances.  Users’ experience and the improvement of it is still high up in the customer requirement list, even under the constraints of power consumption consideration.  Both ext4 and Brtfs answer to the issue and their adoptions by smart phones and tablet PCs are quite foreseeable, in SmartMobix’s


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