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Ext4 Filesystem Enters Experimental Kernel Tree 237

Posted by timothy
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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  • Reiser4 (Score:3, Funny)

    by Anonymous Coward on Friday October 13, 2006 @08:10AM (#16421471)
    Unfortunately, this will just murder Reiser4.
  • by BenBenBen (249969) on Friday October 13, 2006 @08:17AM (#16421505)
    1 Exabyte!

    Not to be confused with Excitebike, which is something entirely different.
    • Re: (Score:3, Insightful)

      by entrylevel (559061)
      Insightful? Yes. Informative? Certainly not. Finally the Funny mod hits (what took so long?) This is the funniest thing I've read on Slashdot in ages, on so many levels.

      On second thought, maybe it is Informative, since I was not previously aware you could cram that many puns into so few words.
    • Oh! If only they could have squeezed an extra 4 petabyes on so that we could get a true exabyte. What am I to do with my last 4PB of... um... art?
    • Re: (Score:2, Funny)

      by ndsbriand (870862)
      BenBenBen wrote:
      1 Exabyte!
      You are hereby notified to refrain from using our trademark in such a manner. If such pratices continue, we may be forced to take legal action.

      Regards,


      Exabyte Corporation
  • fsck (Score:5, Funny)

    by tttonyyy (726776) on Friday October 13, 2006 @08:19AM (#16421537) Homepage Journal
    EXT4-fs warning (device sdb1): ext4_journal_start_sb: Detected tasteless ReiserFS jokes - hahahaha!
  • FSCK (Score:2, Troll)

    by Pegasus (13291)
    Wake me up when chunkfs hits the kernel. I don't even want to think about fscking all those petabytes ...
    • by walt-sjc (145127)
      Yeah - it's brutal to fsck a 1T array, or even just mkfs a partition that large with ext3. XFS and JFS are MUCH MUCH faster. So besides just huge filesystems, what else is better about ext4?
      • by Abcd1234 (188840)
        Well, given ext4 (like ext3) is journalled, I can't see why you'd ever perform a full fsck (unless you're paranoid).
        • by rubycodez (864176)
          sometimes the extX force you to do an fsck before it'll mount, let's face it, it's not as sophisticated as other more advanced fs
  • 1020 petas (Score:2, Funny)

    by blantonl (784786)
    >> 1020 petabytes

    My porn collection will now be complete.
    • by Zaatxe (939368) on Friday October 13, 2006 @09:08AM (#16421927)
      >> 1020 petabytes
      My porn collection will now be complete.


      Liar... there is no such thing as a complete porn collection!
    • Re: (Score:2, Interesting)

      My porn collection will now be complete
      In fact, 315 TB should be enough for anybody.

      Here is why:
      Suppose you want to watch porn 24 hours a day from the age of 15 till 75. Thats 60 years = 60 * 365.25 * 24 * 60 * 60 s = 1.89 * 10^9 s
      A DivX is around 600 MB / hour = 600 * 1000000 / (60 * 60) = 1.67 * 10^5 B/s
      So for your lifetime porn collection you need 1.89 * 1.67 * 10^14 B = 315 TB.
      • You're neglecting the possibility for VR formats.

        I'm sure full-immersion sensory data will require far more data bandwidth.
      • by nuzak (959558)
        > In fact, 315 TB should be enough for anybody.

        No, 2^128 bits should be enough for anybody [sun.com]. Everybody, in fact.
      • by ArwynH (883499)

        What SD Porn?! With artifacts?! True Pron addicts will only settle for 1080p HQ porn!

        Mind you, even that won't take up 1024 PB... maybe if you used raw video with no compression...

      • by joto (134244)
        You forgot something. You need to skip the boring parts. Assuming you only watch about 10% of the porn, and skip past the rest, you need 3150TB. And of course, you may want something a little higher definition than the typical 2006 DivX. In twenty years time, I'll probably want a fully immersive experience, with a tactile VR suit. This will need much higher bandwidth (or is it called "wider bandwidth"? ;-)
    • by Wiz (6870)
      Ah, don't you mean the index to your porn collection with be complete? ;)
  • performance (Score:4, Interesting)

    by bioglaze (767105) on Friday October 13, 2006 @08:24AM (#16421579) Homepage Journal
    How does ext4 perform when compared to, say, reiserfs 3.6 or 4? What new features there are?
  • 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?
    • Re: (Score:3, Interesting)

      by Zarhan (415465)
      Ofcourse people can do whatever they want, but why not spend their time making XFS easily resizable for example?

      I would also appreciate block journaling for XFS.
    • Re: (Score:2, Insightful)

      by orzetto (545509)
      (exabyte = 1024 petabytes).

      You mean, "exbibyte = 1024 pebibyte". An exabyte is exactly 1000 petabyte.

      I used to think this was just fussy, but I am quite tired of guessing which system producers of hard disks/CDROMs/DVD+±×RWs use to figure out if that is enough for my needs.

    • by Spirilis (3338)
      Can't you grow an XFS online already? In fact, that's the only way you can grow an XFS filesystem... with it mounted.
    • I think the main advantage over XFS is that the codebase won't make kernel developers vomit.

      From a user POV, XFS is my favorite FS, and I've had no bad experiences with it whatsoever. However, from what I've heard about the code, I can fully understand why it's not "popular" among kernel devs, and why none of the enterprise distros favor it (because doing so would inevitably force _their_ kernel hackers to try to debug XFS-related errors).
      I'm hoping now that SGI is officially "retiring" IRIX, XFS will be cl
    • 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).
  • Wow (Score:3, Funny)

    by knipknap (769880) on Friday October 13, 2006 @08:33AM (#16421683) Homepage
    enabling Linux to support storage volumes up to 1020 petabytes in size

    Now, is there anybody who still believes that porn does not drive innovation?
  • also in linus tree (Score:2, Informative)

    by alonso (63617)
    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).
  • And how... (Score:5, Insightful)

    by porkchop_d_clown (39923) <mwheinzNO@SPAMme.com> on Friday October 13, 2006 @08:42AM (#16421755) Homepage
    Will we back all this data up?

    I'm honestly more interested in someone coming up with cheap, long term archival storage. Hard disks have gone so far past our ability to archive information it's beyond comprehension.
    • by CastrTroy (595695)
      Well, you could just back everything up on other hard drives, instead of using tapes or whatever else you are used to. Sure hard drives crash, but not when you just write the backup to them and then put them on a shelf. I don't think they'd be any less dependable than tapes.
    • by Eivind (15695)
      I don't see the problem.

      Harddiscs are, as you say currently superior to other storage-technologies.

      So, you make backups to hard-disc then. Simple. Quick. Affordable.

      Yes, the lifetime is limited, so you should make sure to have atleast 2 independent backups (that's true for any media, all media can go bad) and you should change them every 3 years or so.

      The thing is, capacity is growing so rapidly, that in 3 years, what is now a hard-disc full of backup will be a hard-disc 10% full of backup.

      I need

    • by Zaatxe (939368)
      Will we back all this data up?

      20 years ago you would ask the same thing about 500 MB hard disks. And don't forget the article (or at least the sumary, as a good slashdotter I don't RTFA) says about the file system capacity, not the real capacity of hard disks. Petabytes hard disks are something for the future, not for now.
      • Dude, who had 500MB drives in 1986?
        I saw 50 meg drives that were 18" platters and scarry big.

        I'd think your point still is valid though...
        Anyone in 1986 faced with the prospect of backing up 500Mb would likely turn to the intern and say: "Start memorizing".

        BTW, in 1986 if someone came up to you and told you that there would be hard drives in 20 years that are 750GB and were faster than your current system memory what would you have said to them?
        -nB
        • by Zaatxe (939368)
          Dude, who had 500MB drives in 1986?
          Hmmm... aliens? Well, who has 1020 petabytes drives today?

          BTW, in 1986 if someone came up to you and told you that there would be hard drives in 20 years that are 750GB and were faster than your current system memory what would you have said to them?
          I'd say "to the time machine, Robin!"
    • by jdavidb (449077) *

      You buy ten of them and do a super-redundant RAID.

      • by eln (21727) *
        RAID won't help when you accidentally delete half of your database. Tape backups protect against more than just hardware failure.
        • by Abcd1234 (188840)
          Indeed. Just ask my wife, who accidentally did an "rm -rf *" in her mirrored home directory...
          • who wanted to delete some of the preference files in his home directory, so he typed

            rm -rf .*

            It never occurred to him (or me) that ".." matched that pattern. He worked his way right up the directory tree and back down again...
        • It does with ZFS or with FreeBSD's UFS2. Most relatively modern filesystems support snapshots, so all you need to do is set a cron job to regularly mount snapshots and then you can roll things back easily. ZFS is nicer than UFS2 for this, since it allows you to snapshot any part of the directory hierarchy at any point easily, and the copy-on-write mechanism allows for much easier updates.

          If it weren't for the GPL, Linux could just port ZFS over and everyone would be happy.

    • I'm honestly more interested in someone coming up with cheap, long term archival storage. Hard disks have gone so far past our ability to archive information it's beyond comprehension.

      Once, I was like you. Backupless. Then I went down to by local PC store and happened by a 320GB external USB HDD for around 200. Needless to say my current backup woes have been solved. If I ever get around to building that terabyte fileserver, all I need do is lash together four of these little beauties and use something lik

  • "and to write files in 'extents,'"

    Aright! 1970s mainframe technology, here we come!
    • Re: (Score:2, Informative)

      by rjamestaylor (117847)
      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!
    • by gstoddart (321705)
      Aright! 1970s mainframe technology, here we come!

      Given the reputation of 1970's mainframe technology for being bomb-proof, reliable, stable, and useful, I'd say it's about fscking time.

      Just because something was a good idea then, doesn't mean it isn't a good idea now.

      Cheers
  • by Saint Aardvark (159009) * on Friday October 13, 2006 @09:05AM (#16421897) Homepage Journal

    to no longer use ReiserFS [wordpress.com] as its default FS (orig. reported on OSNews.com [osnews.com]...don't think I've seen it here yet). I think this came out before the whole Hans Reiser affair, BTW.

    SuSE contrasted the ease of upgrading ReiserFS and ExtFS versions:

    ReiserFS v3 is a dead end. Hans has been pushing reiser4 for years now and declared Reiser3 in maintenance mode. Any changes that arent bug fixes are met with violent resistance. Reiser4 is not an incremental update and requires a reformat, which is unreasonable for most people.... Ext3 has a clear upgrade path. There is quite a bit of interest in the community in improving ext3, and ext4 is already under development. Like the upgrade path from ext2 to ext3, the path to ext4 is clearly defined. Existing file systems can be updated easily, and new files will be able to take advantage of the new features.
  • Experimental?? (Score:2, Interesting)

    by scsirob (246572)
    What I don't onderstand is that this is merged into the 2.6 kernel tree today. What has happened to the concept of -stable (2.6) and -experimental (2.7) trees? This would be aperfect opportunity to open the next experimental branche..
    • What has happened to the concept of -stable (2.6) and -experimental (2.7) trees?

      They're all equally stable now :-)
    • Well, this was news to me too, but...

      The development model for Linux 2.6 was a significant change from the development model for Linux 2.5. Previously there was a stable branch (2.4) where only relatively minor and safe changes were merged, and an unstable branch (2.5), where bigger changes and cleanups were allowed. This meant that users would always have a well-tested 2.4 version with the latest security and bug fixes to use, though they would have to wait for the features which went into the 2.5 branch

  • Other Reiser issues aside, the SuSE folks at Novell are looking to leave [linux.com] the nearly unsupported reiserfs3 (in maintenance support, which isn't enough for them) and move to ext3 as their default FS. Why? They feel ext3 is a lot more mature & better/wider supported then reiserfs4, is an easier migration, and appreciate that there is a solid roadmap from ext3 to ext4.

    Of course this would also be the week that (coincidentally) Andrew Morton gives reiserfs4 the green light [apcstart.com] for eventual mainline kernel inclusion.

  • 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 [lkml.org] for a more detailed description of what is happening.

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

      by l4m3z0r (799504)

      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 m

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