Info about EXT and partitioning?

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  1. Lipz

    Lipz Member

    Every time I customize a device, I most likely will come across the "Partition SD/Memory Stick Duo". I never really thought about until now, but what exactly is this? Even more so, I notice that i can choose an amount of MB(a2sd) and place anything from the Dalvik to an app on it, which leads into my next question: What is EXT? Any info is appreciated and thanks in advance :)

  2. karandpr

    karandpr Well-Known Member

    EXT is a filesystem like FAT32/NTFS
    EXT2/3/4 are usually used in Linux/androids

    ext2 is fast but lacks journal-ling so fsck should be done time to time

    ext4 is slower but has journals (I think) and is much more advanced .fsck is faster in ext2

    There are also xfs , JFS(Preferred for /data,/cache ) ,reiserfs (faster read ,ideal for /system).

    Research from
    Partition capacity

    Initial (after filesystem creation) and residual (after removal of all files) partition capacity was computed as the ratio of number of available blocks by number of blocks on the partition. Ext3 has the worst inital capacity (92.77%), while others FS preserve almost full partition capacity (ReiserFS = 99.83%, JFS = 99.82%, XFS = 99.95%). Interestingly, the residual capacity of Ext3 and ReiserFS was identical to the initial, while JFS and XFS lost about 0.02% of their partition capacity, suggesting that these FS can dynamically grow but do not completely return to their inital state (and size) after file removal.
    Conclusion : To use the maximum of your partition capacity, choose ReiserFS, JFS or XFS.

    File system creation, mounting and unmounting

    The creation of FS on the 20GB test partition took 14.7 secs for Ext3, compared to 2 secs or less for other FS (ReiserFS = 2.2, JFS = 1.3, XFS = 0.7). However, the ReiserFS took 5 to 15 times longer to mount the FS (2.3 secs) when compared to other FS (Ext3 = 0.2, JFS = 0.2, XFS = 0.5), and also 2 times longer to umount the FS (0.4 sec). All FS took comparable amounts of CPU to create FS (between 59% - ReiserFS and 74% - JFS) and to mount FS (between 6 and 9%). However, Ex3 and XFS took about 2 times more CPU to umount (37% and 45%), compared to ReiserFS and JFS (14% and 27%).
    Conclusion : For quick FS creation and mounting/unmounting, choose JFS or XFS.

    Operations on a large file (ISO image, 700MB)

    The initial copy of the large file took longer on Ext3 (38.2 secs) and ReiserFS (41.8) when compared to JFS and XFS (35.1 and 34.8). The recopy on the same disk advantaged the XFS (33.1 secs), when compared to other FS (Ext3 = 37.3, JFS = 39.4, ReiserFS = 43.9). The ISO removal was about 100 times faster on JFS and XFS (0.02 sec for both), compared to 1.5 sec for ReiserFS and 2.5 sec for Ext3! All FS took comparable amounts of CPU to copy (between 46 and 51%) and to recopy ISO (between 38% to 50%). The ReiserFS used 49% of CPU to remove ISO, when other FS used about 10%. There was a clear trend of JFS to use less CPU than any other FS (about 5 to 10% less). The number of minor page faults was quite similar between FS (ranging from 600 - XFS to 661 - ReiserFS).
    Conclusion : For quick operations on large files, choose JFS or XFS. If you need to minimize CPU usage, prefer JFS.

    Operations on a file tree (7500 files, 900 directories, 1.9GB)

    The initial copy of the tree was quicker for Ext3 (158.3 secs) and XFS (166.1) when compared to ReiserFS and JFS (172.1 and 180.1). Similar results were observed during the recopy on the same disk, which advantaged the Ext3 (120 secs) compared to other FS (XFS = 135.2, ReiserFS = 136.9 and JFS = 151). However, the tree removal was about 2 times longer for Ext3 (22 secs) when compared to ReiserFS (8.2 secs), XFS (10.5 secs) and JFS (12.5 secs)! All FS took comparable amounts of CPU to copy (between 27 and 36%) and to recopy the file tree (between 29% - JFS and 45% - ReiserFS). Surprisingly, the ReiserFS and the XFS used significantly more CPU to remove file tree (86% and 65%) when other FS used about 15% (Ext3 and JFS). Again, there was a clear trend of JFS to use less CPU than any other FS. The number of minor page faults was significantly higher for ReiserFS (total = 5843) when compared to other FS (1400 to 1490). This difference appears to come from a higher rate (5 to 20 times) of page faults for ReiserFS in recopy and removal of file tree.
    Conclusion : For quick operations on large file tree, choose Ext3 or XFS. Benchmarks from other authors have supported the use of ReiserFS for operations on large number of small files. However, the present results on a tree comprising thousands of files of various size (10KB to 5MB) suggest than Ext3 or XFS may be more appropriate for real-world file server operations. Even if JFS minimize CPU usage, it should be noted that this FS comes with significantly higher latency for large file tree operations.

    Directory listing and file search into the previous file tree

    The complete (recursive) directory listing of the tree was quicker for ReiserFS (1.4 secs) and XFS (1.8) when compared to Ext3 and JFS (2.5 and 3.1). Similar results were observed during the file search, where ReiserFS (0.8 sec) and XFS (2.8) yielded quicker results compared to Ext3 (4.6 secs) and JFS (5 secs). Ext3 and JFS took comparable amounts of CPU for directory listing (35%) and file search (6%). XFS took more CPU for directory listing (70%) but comparable amount for file search (10%). ReiserFS appears to be the most CPU-intensive FS, with 71% for directory listing and 36% for file search. Again, the number of minor page faults was 3 times higher for ReiserFS (total = 1991) when compared to other FS (704 to 712).
    Conclusion : Results suggest that, for these tasks, filesystems can be regrouped as (a) quick and more CPU-intensive (ReiserFS and XFS) or (b) slower but less CPU-intensive (ext3 and JFS). XFS appears as a good compromise, with relatively quick results, moderate usage of CPU and acceptable rate of page faults.


    These results replicate previous observations from Piszcz (2006) about reduced disk capacity of Ext3, longer mount time of ReiserFS and longer FS creation of Ext3. Moreover, like this report, both reviews have observed that JFS is the lowest CPU-usage FS. Finally, this report appeared to be the first to show the high page faults activity of ReiserFS on most usual file operations.

    While recognizing the relative merits of each filesystem, only one filesystem can be install for each partition/disk. Based on all testing done for this benchmark essay, XFS appears to be the most appropriate filesystem to install on a file server for home or small-business needs :

    It uses the maximum capacity of your server hard disk(s)
    It is the quickest FS to create, mount and unmount
    It is the quickest FS for operations on large files (>500MB)
    This FS gets a good second place for operations on a large number of small to moderate-size files and directories
    It constitutes a good CPU vs time compromise for large directory listing or file search
    It is not the least CPU demanding FS but its use of system ressources is quite acceptable for older generation hardware

    BTRFS is Fastest but is CPU hungry in turn it affects battery .It''s better than JFS. Very nice for second SD card partition (Currently using)

    Reiser4FS is closely related to BTRFS and has almost equal performance .It has faster Read rate making it ideal for ro /system

    JFS is ideal for /data and /cache since it has slower read than reiserfs but way faster write than reseirfs .It has the least cpu usage in all FS.

    Currently I am trying to see xfs instead of btrfs and see it's impact .

    ReiserFS ,BTRFS ,XFS,JFS,ext2/3/4 all need to fsck to function properly .

    Hope this helps :)


    Forgot about partitioning .
    you will need mkfs binary for formating in /system/bin folder or symlinked to busybox
    mkfs.ext2, mkfs.ext3, , mkfs.vfat, mkfs.xfs, mkfs.jfs and so on
    usually second SD partition is /dev/block/mmcblk0p2

    for ext2
    mkfs.ext2 -m 0 -b 4096 /dev/block/mmcblk0p2
    should do the trick .

    Gparted partition wizard for ext2/3/4

    or mini tools partition wizard /EASEUS for windows ext 2/3/4 partition .
    Lipz likes this.
  3. SUroot

    SUroot Well-Known Member Developer

    See signature to see how much I agree with you ;)
  4. karandpr

    karandpr Well-Known Member

    Haha ,
    I am currently using fdisk and busybox-mkfs combo batch script .
    Ok I am lying ,Only the mkfs batch script .I dont have enough patience to reformat my SD card ;)
  5. Lipz

    Lipz Member

    Thanks for the info. :) I have alot to do lol

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