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On Wed, May 28, 2014 at 11:26 AM, Bob Sanders <rsanders@×××.com> wrote: |
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> Marc Joliet, mused, then expounded: |
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>> Am Tue, 27 May 2014 15:39:38 -0700 |
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>> schrieb Bob Sanders <rsanders@×××.com>: |
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>> |
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>> While I am far from a filesystem/storage expert (I see myself as a mere user), |
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>> the cited threads lead me to believe that this is most likely an |
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>> overhyped/misunderstood class of errors (e.g., posts [1] and [2]), so I would |
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>> suggest reading them in their entirety. |
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>> |
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>> [0] http://comments.gmane.org/gmane.comp.file-systems.btrfs/31832 |
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>> [1] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/31871 |
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>> [2] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/31877 |
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>> [3] http://comments.gmane.org/gmane.comp.file-systems.btrfs/31821 |
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>> |
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> |
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> FWIW - here's the FreeNAS ZFS ECC discussion on what happens with a bad |
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> memory bit and no ECC memory: |
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> |
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> http://forums.freenas.org/index.php?threads/ecc-vs-non-ecc-ram-and-zfs.15449/ |
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> |
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|
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I don't think that anybody debates that if you use btrfs/zfs with |
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non-ECC RAM you can potentially lose some of the protection afforded |
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by the checksumming. |
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What I'd question is that this is some concern unique to btrfs/zfs. |
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I'd think the same failure modes would all apply to any other |
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filesystem. |
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So, the message should be that ECC RAM is better than non-ECC RAM, not |
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that those who use non-ECC RAM are better off using ext4 instead of |
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zfs/btrfs. I'd think that any RAM-related issue that would impact |
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zfs/btrfs would affect ext4 just as badly, and with ext4 you're also |
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vulnerable to all the non-RAM-related errors that checksumming was |
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created to solve. |
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|
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If your RAM is bad then all kinds of stuff can go wrong. Ditto for |
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your cache memory in the CPU, logic circuitry in the CPU, your busses, |
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etc. Most systems are not fault-tolerant of these system components |
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and the cost to make them fault-tolerant tends to be fairly high. On |
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the other hand, the good news is that you're far more likely to have |
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problems with data stored on a disk than in RAM, which is probably why |
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we haven't bothered to improve the other components. |
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|
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Rich |
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