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c.f. bug 424647
List Archive: gentoo-embedded
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To: gentoo-embedded@g.o
From: Ed W <lists@...>
Subject: Re: quickpkg and PKG_INSTALL_MASK
Date: Fri, 27 Jan 2012 18:27:45 +0000
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    On 26/01/2012 14:59, Peter Stuge wrote:<br>
    <blockquote cite="mid:20120126145920.20149.qmail@..."
      type="cite">
      <blockquote type="cite">
        <pre wrap="">I do have the impression that any block emulating device such as
SSD are unreliable w.r.t power cuts. I would love to be proven
wrong though :)
</pre>
      </blockquote>
      <pre wrap="">
Supposedly, Intel SSDs never report write completed before flash has
actually been updated. Good luck verifying that.

Everyone else buffers writes. The Samsung 830 series has 256MB of
SDRAM, and their multicore ARM controller handles the magic
buffering. Samsung 830 is built entirely by Samsung from Samsung
parts. All manufacturers besides Intel and Samsung use a mishmash
of components and firmware in their SSD products, and all do magic
buffering.</pre>
    </blockquote>
    <br>
    I can't find a reference right now, but I am under the impression
    that the more expensive "enterprise" SSD modules now have some
    battery backup onboard to allow writes to complete in sudden power
    down situations?&nbsp; I read recently of one consumer report (probably
    on Anand tech, but can't find it now...) which had also been fitted
    with some kind of supercap to handle unexpected powerloss<br>
    <br>
    (Update, google "SSD supercap" - seems like some of the higher end
    Sandforce boards have such a thing, and on skimming it is implied
    that the Vertex3 might have such a thing?)<br>
    <br>
    I also found this paper which seemed interesting:<br>
    &nbsp;&nbsp;&nbsp; <a class="moz-txt-link-freetext" href="http://cseweb.ucsd.edu/users/swanson/papers/DAC2011PowerCut.pdf">http://cseweb.ucsd.edu/users/swanson/papers/DAC2011PowerCut.pdf</a><br>
    <br>
    <br>
    Seems like it's a rocky road ahead...<br>
    <br>
    Cheers<br>
    <br>
    Ed W<br>
    <br>
    <br>
    P.S.&nbsp; I think this phenomena explains what surely everyone here has
    experienced, that if you rip out a USB flash drive while it's still
    writing then every so often the whole drive just disappears (and
    stays dead)?&nbsp; Also I have killed one CF almost certainly due to a
    sudden reboot (but it was the design that has since been recalled by
    PCEngines), and a few others that on reflection might have had a
    sudden powerdown in a camera or while removing pictures from the
    camera flash card...&nbsp; Read random amazon reviews of flash drives and
    there are always a bunch of people who post when their drive totally
    fails while it's new - again my bet would be many of these would be
    explained by sudden unplugs during write...<br>
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References:
quickpkg and PKG_INSTALL_MASK
-- Joakim Tjernlund
Re: quickpkg and PKG_INSTALL_MASK
-- Kfir Lavi
Re: quickpkg and PKG_INSTALL_MASK
-- solar
Re: quickpkg and PKG_INSTALL_MASK
-- Joakim Tjernlund
Re: quickpkg and PKG_INSTALL_MASK
-- Ed W
Re: quickpkg and PKG_INSTALL_MASK
-- Joakim Tjernlund
Re: quickpkg and PKG_INSTALL_MASK
-- Todd Goodman
Re: quickpkg and PKG_INSTALL_MASK
-- Ed W
Re: quickpkg and PKG_INSTALL_MASK
-- Joakim Tjernlund
Re: quickpkg and PKG_INSTALL_MASK
-- Peter Stuge
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Updated Jun 25, 2012

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