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Thread: There's Talk Again About Btrfs For Fedora

  1. #61
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    Quote Originally Posted by jwilliams View Post
    The fact that btrfs is not used as default in any widely-trusted OS means that btrfs is not trustworthy.
    So XFS is not "trustworthy" either because it's not a default in any "widely-trusted" OS even though it has been developed and used for the past 17 years? You would think that there would be a better way to evaluate the realiability of a file system than just looking if it's used by some general purpose operaiting system.

  2. #62
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    Quote Originally Posted by smitty3268 View Post
    ...btrfs isn't as solid as ZFS was...
    Snipped all your jabbering to quote the important thing.

    btrfs is not as solid as ZFS was. Understatement. btrfs is not solid at all.

  3. #63
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    Quote Originally Posted by Teho View Post
    So XFS is not "trustworthy" either because it's not a default in any "widely-trusted" OS
    Bad assumptions.

    1) XFS was default on Irix

    2) XFS offers very little in additional features over common default filesystems (unlike btrfs which has several additional features) so there is little reason to make a change to XFS -- therefore XFS is a bad example.

  4. #64

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    Quote Originally Posted by GreatEmerald View Post
    Nope. What they are saying is that due to the fact that ZFS was developed by the same company that developed Solaris, they are clearly biased towards it. Thus the fact that it's used by default on Solaris does not mean that ZFS is trustworthy.
    ZFS is by no means perfect, but it has several data integrity features:

    1. ZFS stores everything in a hash tree, so integrity of all nodes can be verified with the assumption that no hash collision has occurred. 256-bit (SHA256) hashes are used, so it is unlikely that a single collision will ever happen across all systems on which ZFS is deployed for the duration of the universe.
    2. ZFS stores metadata twice via "ditto blocks". It makes an effort to write metadata at least 1/8 of the disk apart, so random corruption will have to take out two of the same metadata block before it can damage a filesystem.
    3. ZFS utilizes copy on write to implement atomic transactions, which involve a two stage transaction commit. This involves the disk labels, which store 4 copies of the uberblock. The uberblock is ZFS' equivalent of a superblock Two labels are located at the beginning of the disk and two labels are located at the end of the disk. A transaction commit will first update labels 0 and 2 and then labels 1 and 3, which ensures atomicity.
    4. ZFS maintains history of the last N uberblocks, which permits rollback to an older entry should malfunctioning hardware cause a write to become inconsistent.
    5. ZFS recycles blocks only after a certain number of transactions have occurred, so rollback is guaranteed to be possible.


    btrfs cannot really compare to this. My understanding of btrfs is somewhat superficial, but lets compare:

    1. btrfs' uses hashes as well, but it has 32-bit hashes on 32-bit userlands and 64-bit hashes on 64-bit userlands. As long as there are no collisions, you can verify the integrity of data, but the probability of a collision is quite high, especially in the 32-bit case.
    2. btrfs has no ditto blocks, so if metadata is corrupted, there is a strong possibility that it will be unable to recover.
    3. btrfs does attempt atomic transactions, but it is single stage. In SSD mode, it only stores a single copy of the superblock. If the primary superblock becomes corrupted, the kernel will no longer recognize it.
    4. btrfs does not maintain much of a history. It has two pointers. One for the last transaction and one for its predecessor. If malfunctioning hardware corrupts the last two transactions (due to incomplete flushes), btrfs cannot recover.
    5. btrfs does no automated rebalancing, so rollback is probably possible on it. However, if you do a rebalance, I do not know if it will be possible to do rollback.


    Feel free to post corrections. I admit that my knowledge of btrfs is somewhat lacking, but I believe that what I have said is accurate.

    Quote Originally Posted by Teho View Post
    So XFS is not "trustworthy" either because it's not a default in any "widely-trusted" OS even though it has been developed and used for the past 17 years? You would think that there would be a better way to evaluate the realiability of a file system than just looking if it's used by some general purpose operaiting system.
    It is an open secret that no filesystem is perfect. If you have perfectly functioning hardware, then it is possible to prove program correctness, but it is incredibly difficult to do that and so far no one has done it for a filesystem to my knowledge. Since hardware is imperfect, proving correct operation (with in some constraints) is even harder. To put it simply, some filesystem software is more prone to problems than others.

  5. #65
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    Quote Originally Posted by jwilliams View Post
    btrfs is ... solid
    Hey look, i can do out of context selective quoting to!

    I snipped all your jabbering for you there. Your welcome.
    Last edited by smitty3268; 01-18-2013 at 08:42 PM.

  6. #66
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    Quote Originally Posted by smitty3268 View Post
    I snipped all your jabbering for you there.
    The difference is, you were jabbering and blathering on about nonsense, and I wrote concisely and to the point. Another difference is that you misquoted me by leaving out a word in the middle of a phrase.

    You can put your hands over your ears and hum all you want, but the bottom line is that btrfs is untrustworthy.

  7. #67
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    Quote Originally Posted by jwilliams View Post
    You can put your hands over your ears and hum all you want, but the bottom line is that btrfs is untrustworthy.
    May I ask a question jwilliams? Which one of your relations did Chris Mason bash over the head with a shovel and then buried in your backyard? Because that is the only reason I can see for why you are getting such a bee in your bonnet here.

    You do not like btrfs. Fine. Why get into this argument?

  8. #68
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    Quote Originally Posted by jwilliams View Post
    The difference is, you were jabbering and blathering on about nonsense, and I wrote concisely and to the point.
    Is English not your native language, or what are you smoking? I made a clear point, you're the one speaking in circles and blathering on and on and on.

    Another difference is that you misquoted me by leaving out a word in the middle of a phrase.
    Is that somehow supposed to be worse than misquoting me by leaving out multiple words before and after a phrase? LOL

    You can put your hands over your ears and hum all you want, but the bottom line is that btrfs is untrustworthy.
    Yeah, I get it. You're going to keep trolling by repeating the same line over and over until everyone gets tired. I once employed the same tactic against Qaridarium. It was pretty glorious.

  9. #69
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    Quote Originally Posted by Hamish Wilson View Post
    Why get into this argument?
    Why not? Why did you post the comment asking me about it?

  10. #70
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    Quote Originally Posted by smitty3268 View Post
    Is that somehow supposed to be worse than misquoting me by leaving out multiple words before and after a phrase? LOL
    Are you incapable of rational thought as well as being unable to post anything except nonsense? LOL

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