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Btrfs Is Getting There, But Not Quite Ready For Production

Posted by timothy on from the delicious-on-popcrnfs dept.

An anonymous reader writes "Btrfs is the next-gen filesystem for Linux, likely to replace ext3 and ext4 in coming years. Btrfs offers many compelling new features and development proceeds apace, but many users still aren't sure whether it's 'ready enough' to entrust their data to. Anchor, a webhosting company, reports on trying it out, with mixed feelings. Their opinion: worth a look-in for most systems, but too risky for frontline production servers. The writeup includes a few nasty caveats that will bite you on serious deployments."

8 of 268 comments (clear)

  1. Read their website by Anonymous Coward · · Score: 5, Informative

    It says "experimental." They appreciate you helping them test their file system out. I appreciate it too, so please do. But remember that you are testing an experimental filesystem. When it eats your data, make sure you report it and have backups.

    1. Re:Read their website by pipatron · · Score: 5, Informative

      Every file system is/should be labled "experimental" in a way. The long answer from the btrfs FAQ is pretty good, and makes some sense:

      Long answer: Nobody is going to magically stick a label on the btrfs code and say "yes, this is now stable and bug-free". Different people have different concepts of stability: a home user who wants to keep their ripped CDs on it will have a different requirement for stability than a large financial institution running their trading system on it. If you are concerned about stability in commercial production use, you should test btrfs on a testbed system under production workloads to see if it will do what you want of it. In any case, you should join the mailing list (and hang out in IRC) and read through problem reports and follow them to their conclusion to give yourself a good idea of the types of issues that come up, and the degree to which they can be dealt with. Whatever you do, we recommend keeping good, tested, off-system (and off-site) backups.

      --
      c++; /* this makes c bigger but returns the old value */
    2. Re:Read their website by Bengie · · Score: 4, Informative

      My cousin said when he had to go "FS shopping" for his research data center, they had some requirements, most notably, being used by several enterprises that all store at least 1PB of data on the FS and have not had any critical issues in 5 years.

      He said the only FS that fit-the-bill was ZFS. His team could not find an enterprise company that stored at least 1PB of data on ZFS and had a non-user caused critical problem within the past 5 years. That was many years ago and he has not had a single issue with his multi-PB storage that is being used by hundreds of departments.

      ZFS is not perfect, but it sets a very high bar.

    3. Re:Read their website by Zero__Kelvin · · Score: 5, Informative

      Did your cousin also find out what exact hardware and exact code was used? If my friend has had no problems with filesystem $FS and then I use it with different hardware and code implementing it, then there is still a significant chance that I will have trouble that he did not. Filesystems all work perfectly, because they are conceptual. It is the implementation that may or may not be stable.

      --
      Guns don't kill people; Physics kills people! - John Lithgow as Dick Solomon on Third Rock From The Sun
  2. ZFS by 0100010001010011 · · Score: 5, Informative

    Meanwhile ZFS announced that it was ready for production last month.

    http://zfsonlinux.org/

  3. Re:Happy with XFS by MBGMorden · · Score: 5, Informative

    Your happy with XFS because your machine has never lost power or crashed. If either of those things happened with the older versions of XFS it was nearly a 100% guarantee you would lose data. Now i'm told its more reliable.

    I don't know about being more reliable. I use XFS on my RAID array (mdadm) at home. I'm running the latest version of Linux Mint (Nadia), and if I ever lose poser and don't unmount that file system cleanly it looses all recent changes to the drive (and "recent" sometimes stretches to hours ago). The drive mounts fine and nothing appears corrupted (so I guess its not completely data loss), but any files changes (edits, additions, or deletions) to the file system are simply gone.

    Its gotten to the point where if I've just put a lot of stuff on the drive I unmount it and then remount it just to make sure everything gets flushed to disk. If I ever get a chance to rebuild that array it most certainly will be using something different.

    --
    "People who think they know everything are very annoying to those of us who do."-Mark Twain
  4. Re:Happy with XFS by Booker · · Score: 4, Informative

    No, that's FUD and/or misunderstanding on your part.

    "data=ordered" is ext3/4's name for "don't expose stale data on a crash," something which XFS has never done, with or without a mount option. ext3/4 also have "data=writeback" which means "DO expose stale data on a crash." XFS does not need feature parity for ill-advised options.

    Any filesystem will lose buffered and unsynced file data on a crash (http://lwn.net/Articles/457667/). XFS has made filesystem integrity and data persistence job one since before ext3 existed. Like any filesystem, it has had bugs, but implying that it was unsafe for use until recently is incorrect.

    I say this as someone who's been working on ext3, ext4 and xfs code for over a decade, combined.

  5. Re:Happy with XFS by Booker · · Score: 4, Informative

    So, until your understand this basic idea, don't go claiming you know _ANYTHING_ about filesystems.

    Without sounding like too much of a jerk, I have hundreds of commits in the linux-2.6 fs/* tree. This is what I do for a living.
    I actually do have a pretty decent grasp of how Linux journaling filesystems behave. :)

    Test your assumptions on ext4 with default mount options. Create a new file and write some buffered data to it, wait 5-10 seconds, punch the power button, and see what you get. (You'll get a 0 length file) Or write a pattern to a file, sync it, overwrite with a new pattern, and punch power. (You'll get the old pattern). Or write data to a file, sync it, extend it, and punch power. (You'll get the pre-extension size). Wait until the kernel pushes data out of the page cache to disk, *then* punch power, and you'll get everything you wrote, obviously.

    XFS and ext4 behave identically in all these scenarios. Maybe you can show me a testcase where XFS misbehaves in your opinion? (bonus points for demonstrating where XFS actually fails any posix guarantee).

    Yes, ext3/4 have data=journaled - but its not default, and with ext4, that option disables delalloc and O_DIRECT capabilities. 99% of the world doesn't run that way; it's slower for almost all workloads and TBH, is only lightly tested.

    Yes, ext3's data=ordered pushes out tons of file data on every journal commit. That has serious performance implications, but it does shorten the window for buffered data loss to the journal commit time.

    You want data persistence with a posix filesystem? Use the proper data integrity syscalls, that's all there is to it.