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Ext4 Filesystem Enters Experimental Kernel Tree 237

An anonymous reader writes "Looks like the next version of the venerable Linux 'ext' filesystem is just around the corner. Andrew Morton has added an early version of ext4 to his 2.6.19-rc1-mm1 tree, enabling Linux to support storage volumes up to 1020 petabytes in size, and to write files in 'extents,' or contiguous, reserved areas. According to an article at Linux-Watch, ext4 will be ready for production use within six to nine months, if all goes well. On the downside, the new ext4 filesystem will offer only limited backward compatibility with ext3-aware Linux kernels."
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Ext4 Filesystem Enters Experimental Kernel Tree

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  • by Anonymous Coward on Friday October 13, 2006 @08:24AM (#16421591)
    I thought file systems were typically constructed in, for and with software.
  • by Tribbin ( 565963 ) on Friday October 13, 2006 @08:25AM (#16421611) Homepage
    My question is why they don't mention why it is better to use ext4 then XFS.

    XFS can do 9 exabytes (exabyte = 1024 petabytes).

    They mention that ext4 is not faster than other filesystems.

    Ofcourse people can do whatever they want, but why not spend their time making XFS easily resizable for example?
  • also in linus tree (Score:2, Informative)

    by alonso ( 63617 ) on Friday October 13, 2006 @08:34AM (#16421695)
    From lwn current issue(you have to subscribe for the full article ;):

    Also merged is the developmental ext4 filesystem, which includes a number of enhancements, including support for extents and 48-bit block numbers. See the ext4 documentation file if you are interested in playing with ext4 (and have good backups).
  • Re:1020 Petabytes? (Score:4, Informative)

    by HerrEkberg ( 971000 ) on Friday October 13, 2006 @08:54AM (#16421821) Homepage
    Well, that depends on what your expectations for the future are. I don't think it is impossible that demands on multimedia will reach high enough sometime. Let us as an example consider a movie file from the Future (tm). Given better and bigger screens (perhaps covering whole walls) a frame dimension of 3000 x 2000 pixels is not inconceivable. Each pixel might consist of three RGB values of 16 bits each. Such a movie, if two hours long and running with 25 frames / second, would require about 6.5 TB in raw format.

    framedimensions = 3000 x 2000
    framebytes = framedimensions x 6
    moviebytes = framebytes x 25 x 60 x 120

    moviebytes / 10^12 ~= 6.5
  • Re:extents (Score:2, Informative)

    by rjamestaylor ( 117847 ) <> on Friday October 13, 2006 @09:13AM (#16422001) Journal
    Exactly. How well will EXT4 handle CI/CA splits? What userspace tools will exist to tune VSAM, I mean, EXT4 extents?

    With EXT4 having extents we'll finally have the joy of defragmenting a hard drive like Windows people. Yea, progress!
  • Re:1020 Petabytes? (Score:3, Informative)

    by tomstdenis ( 446163 ) <> on Friday October 13, 2006 @09:19AM (#16422085) Homepage
    You forgot the 16 channels of 192KHz 32-bit audio you need to. That's 84GiB on it's own!!! :-)

  • Re:Experimental?? (Score:1, Informative)

    by Slashcrap ( 869349 ) on Friday October 13, 2006 @09:56AM (#16422583)
    What has happened to the concept of -stable (2.6) and -experimental (2.7) trees? []

    You can use the archive function to go back to about two thousand and fucking four. That way you can answer the question yourself instead of everyone else having to go through this tired old shit yet again.
  • by oohshiny ( 998054 ) on Friday October 13, 2006 @10:36AM (#16423151)
    My question is why they don't mention why it is better to use ext4 then XFS.

    Simple: ext4 is a backwards compatible, evolutionary change from ext3, while XFS is a different file system and codebase. XFS doesn't offer sufficient advantages to overcome that built-in advantage of ext4 (after all, neither XFS nor ReiserFS managed to succeed even against ext3).
  • Re:1020 Petabytes? (Score:3, Informative)

    by entrylevel ( 559061 ) <> on Friday October 13, 2006 @12:30PM (#16424919)
    I can't believe I'm answering this, but...
    • Excitebike sounds like exabyte
    • 1020 petabytes != 1 exabyte
    • 1 exbibyte != 1 exabyte
    • In terms of scale, 1 exbibyte and 1 exabyte are completely different, the difference in this kind of mistake could equal several hundred thousand copies of Wikipedia, as opposed to confusing KiB/KB or MiB/MB, which are different, but not earth-vs-sun different.
    • The post was moderated Insightful and then Informative before it was modded Funny
    • I'm counting the excellent sig too
    That's 6, and I'm sure there are more I'm missing... Sorry if you think I'm stretching, but I really think this is one finely crafted layer-joke, and I just enjoy that kind of thing.
  • So funny (Score:3, Informative)

    by augustz ( 18082 ) on Friday October 13, 2006 @12:40PM (#16425125) Homepage
    The article says "On the downside, the new ext4 filesystem will offer only limited backward compatibility with ext3-aware Linux kernels."

    Ext4 is going to be the MOST compatible with Ext3, relative to ANY other option out there.

    Upgrading to Ext4 is NOT going to involve a dump and restore from Ext3, likely a tunefs -j or similar command, just as the ext2 -> ext3 migration worked. Ext4 will be able to mount ext3.

    If older versions of software could use the new format, you wouldn't need the new format. Yes, upgrading to Ext4 means your 120 petabyte raid array will not be compatible with your old "ext3 aware kernel". But it is PRECISELY because such an array is not possible under ext3 that ext4 is going to be introduced.

    And does this submitter think other fancy new filesystems magically work on old kernels? Of course not. Does the submitter know if ext4 will be backported and made available to older releases? It doesn't look like they gave that much thought either.

    Please read this [] for a more detailed description of what is happening.

    Slashdot's always good for a smile.
  • Re:So funny (Score:3, Informative)

    by l4m3z0r ( 799504 ) <> on Friday October 13, 2006 @01:30PM (#16426017)

    The article says "On the downside, the new ext4 filesystem will offer only limited backward compatibility with ext3-aware Linux kernels."

    Well if you had a clue, you would know that this is in reference to the fact that you can mount a ext3 file system as ext2 from a kernel that doesn't have support for ext3. It just doesn't journal. They were simply stating that this rather useful feature that made ext2->ext3 migration so painless will likely not be as simple in ext3->ext4 migration.

    With that in mind, the rest of your post can be safely ignored or moderated into oblivion, thanks for playing!!

  • Re:Reiser4 (Score:3, Informative)

    by udippel ( 562132 ) on Friday October 13, 2006 @09:56PM (#16432951)
    Thanks for the pointer, you are right.

    Though, the author must be a programmer and the reader must count opening and closing quotation. > 80% of the comment is quotation, right, and in the end the author of parent says Even if he is convicted that doesn't mean he is guilty.

    That makes my comment bad, but not the mod. It makes the comment redundant for copy & paste of another post to finally say "I don't agree with this".

Can anyone remember when the times were not hard, and money not scarce?