Re: [gentoo-embedded] quickpkg and PKG_INSTALL_MASK

[Ed W <lists@wildgooses.com>]

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On 26/01/2012 14:59, Peter Stuge wrote:
>> 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 :)
> 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.

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?  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

(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?)

I also found this paper which seemed interesting:
     http://cseweb.ucsd.edu/users/swanson/papers/DAC2011PowerCut.pdf


Seems like it's a rocky road ahead...

Cheers

Ed W


P.S.  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)?  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...  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...

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