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On 26/01/2012 14:59, Peter Stuge wrote: |
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>> I do have the impression that any block emulating device such as |
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>> SSD are unreliable w.r.t power cuts. I would love to be proven |
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>> wrong though :) |
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> Supposedly, Intel SSDs never report write completed before flash has |
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> actually been updated. Good luck verifying that. |
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> |
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> Everyone else buffers writes. The Samsung 830 series has 256MB of |
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> SDRAM, and their multicore ARM controller handles the magic |
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> buffering. Samsung 830 is built entirely by Samsung from Samsung |
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> parts. All manufacturers besides Intel and Samsung use a mishmash |
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> of components and firmware in their SSD products, and all do magic |
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> buffering. |
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I can't find a reference right now, but I am under the impression that |
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the more expensive "enterprise" SSD modules now have some battery backup |
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onboard to allow writes to complete in sudden power down situations? I |
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read recently of one consumer report (probably on Anand tech, but can't |
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find it now...) which had also been fitted with some kind of supercap to |
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handle unexpected powerloss |
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|
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(Update, google "SSD supercap" - seems like some of the higher end |
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Sandforce boards have such a thing, and on skimming it is implied that |
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the Vertex3 might have such a thing?) |
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I also found this paper which seemed interesting: |
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http://cseweb.ucsd.edu/users/swanson/papers/DAC2011PowerCut.pdf |
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Seems like it's a rocky road ahead... |
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Cheers |
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|
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Ed W |
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P.S. I think this phenomena explains what surely everyone here has |
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experienced, that if you rip out a USB flash drive while it's still |
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writing then every so often the whole drive just disappears (and stays |
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dead)? Also I have killed one CF almost certainly due to a sudden |
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reboot (but it was the design that has since been recalled by |
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PCEngines), and a few others that on reflection might have had a sudden |
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powerdown in a camera or while removing pictures from the camera flash |
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card... Read random amazon reviews of flash drives and there are always |
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a bunch of people who post when their drive totally fails while it's new |
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- again my bet would be many of these would be explained by sudden |
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unplugs during write... |