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Google Android Gingerbread Is Using EXT4

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  • Google Android Gingerbread Is Using EXT4

    Phoronix: Google Android Gingerbread Is Using EXT4

    Earlier this year Google announced they would be switching to the EXT4 file-system on their Linux servers (previously they were still using the mature EXT2) and at the same time it was made available they had hired Ted Ts'o, the lead developer of this file-system currently in use by a majority of the new Linux desktop distributions. Google's continuing to love the EXT4 file-system and now with their new Android 2.3 "Gingerbread" operating system for smart-phones and other mobile devices, they are switching to EXT4 there too...

    http://www.phoronix.com/vr.php?view=ODkwMA

  • #2
    Unfortunately a new file system won't do much for certian models such as the Samsung Galaxy S. A couple of our sales reps have them and are on their 4th and 5th replacements despite only having them for only 4 months (memory going bad). (It also happens to be the only android offering the local telco offers).

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    • #3
      Smart phones typically use raw flash devices, which means that the filesystem must implement wear levelling. Ext4 to my knowledge does not implement any wear levelling, so this change will kill smart phones very quickly. It is great for fans of forced obsolescence, but it seems a little evil to me.

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      • #4
        Originally posted by Shining Arcanine View Post
        Smart phones typically use raw flash devices, which means that the filesystem must implement wear levelling. Ext4 to my knowledge does not implement any wear levelling, so this change will kill smart phones very quickly. It is great for fans of forced obsolescence, but it seems a little evil to me.
        Wear leveling really shouldn't be a concern on a smartphone. The amount of read/writes with a typical user would be at pretty much the lowest end of the scale. The average USB key would go through many more read/write cycles and seem to be more reliable. It's not like your going to use a smart phone for daily backups.

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        • #5
          You could also implement wear-leveling at the block level, though. Perhaps they do that?

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          • #6
            Uh. Something is not quite right here. EXT4 and NAND flash devices just are not compatible. Scary that such a prominent developer as Ted can miss this point.

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            • #7
              I suspect that this will only be applied to devices with an ftl device onboard. I just don't see how you could apply ext4 (which is for block devices) to NAND flash (which is a mtd device).

              However recent HTC devices have been using emmc for their storage and ext4 would work there as emmc has the flash controller and nand embedded directly in the same ic.

              I do wonder what performance benefits one would get using ext4 besides having extents.

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              • #8
                Originally posted by manninej View Post
                Uh. Something is not quite right here. EXT4 and NAND flash devices just are not compatible.
                Since when?

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                • #9
                  Most new phones are using block level storage these days. Wear leveling is implemented in hardware. For example, the Nexus S uses an internal SD card for storage. Ext4 is perfectly suited for this as many Galaxy S users can attest.

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                  • #10
                    Originally posted by deanjo View Post
                    Since when?
                    I should have clarified that raw NAND devices are not compatible. If the things are as Dalingrin says then it can be used.

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                    • #11
                      Originally posted by deanjo View Post
                      Since when?
                      Since forever. Unless of course you place an ftl before the nand

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                      • #12
                        Originally posted by _txf_ View Post
                        Since forever. Unless of course you place an ftl before the nand
                        He clarified his post. His original statement was broad and vague.

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                        • #13
                          It's very simple.
                          When using raw flash access, they use YAFFS (they use it on the Nexus S too!!)
                          When using flash that has a disk emulation layer, like the Samsung's oneNand/mNand, then they use EXT4, because YAFFS doesn't work on that, and wear leveling is already implemented at the emulation layer.

                          That's what the Nexus S also uses, and the Galaxy S uses (the SGS only uses that in fact, the Nexus S has a YAFFS part and a EXT4 part)

                          They're both just fine and using EXT4 on top isnt especially always faster or slower than YAFFS, it depends on the chip implementation too.

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                          • #14
                            can only edit post for 1min and phoronixwent down for 2 min when i edited lol..
                            Anyway http://project-voodoo.org/ to make ur SGS use EXT4, its not a bad hardware memory issue but a software bug. Also XXJPU firmware fixes it (but its a beta)

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                            • #15
                              What's the benefit for Phones?

                              Journalled file systems on a flash device make no sense.

                              Most Android phones run in memory anyhow, 512MB if you're lucky to have a phone with that much space in memory.

                              2-16GB file systems are better off with Fat32. Due to copywrite problems they possibly be better off with ext2.

                              1. barrier=0 or barrier=1 ?

                              2. Does Android write data to the file system like Tso says it should?

                              3. fsck.ext4 included in the tools?

                              * When will we get a proper task-killer from G0ogle?

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