risk factor - ext4 and disk corruption

[Kevin Gordon]

For those who, like me, sometimes need a quick refresher read on linux
flash, I always liked this article and its links:

http://www.ibm.com/developerworks/linux/library/l-flash-filesystems/

Cheers

KG



On Wed, Sep 7, 2011 at 12:52 PM, John Watlington <wad at laptop.org> wrote:

>
> The classic trigger for corruption problems (especially w. SD cards)
> is sudden power off events.   I believe we now have the ability
> to tell the EC to auto-power on the laptop, so you can just plug it
> into a lamp timer set to cycle on/off every ten minutes or so
> and let it run...
>
> When you say that the entire 11.2.0 development cycle
> was done with ext4, was that released and abused extensively ?
>
> Cheers,
> wad
>
> On Sep 7, 2011, at 11:06 AM, Martin Langhoff wrote:
>
> > A quick heads up -- we've seen Jon Nettleton hit some disk corruption
> > repeatedly on his development/test machine. Diagnosis of the prob led
> > us to http://dev.laptop.org/ticket/11210 (erase-blocks doesn't work
> > with Toshiba eMMC devices - which is what we have on SKU 198 -
> > membrane kb units) but it is unclear whether that is the issue.
> >
> > This is one of our current risks -- it is a concern because we need to
> > know real soon whether this is a hw issue (related to the eMMC parts)
> > or not. We have hit corruption issues with ext4 in the past (#9513)
> > and fell back to ext3. It is not clear however that ext4 is suspect:
> > the whole 11.2.0 dev cycle was done under ext4 and no disk corruption
> > incidents were reported AFAIK.
> >
> > From IRC discussion -- he seemed to hit it while:
> > - developing, compiling,
> > - using an ext SD card
> > - running a patched kernel and xorg
> > - presumably crashing a lot
> >
> > We need to consider action around this
> >
> > - try to force the error -- I'll set up a test rig for this, applying
> > unclean shutdowns on a couple of SKU198 units
> > - keep our eyes open for disk corruption reports, specially in builds
> > including the new gfx code
> > - potentially switch back to ext3 in OOB
> >
> > It is very hard to prove a negative - tracking this at
> > http://dev.laptop.org/ticket/11220
> >
> > cheers,
> >
> >
> >
> > m
> > --
> >  martin at laptop.org -- Software Architect - OLPC
> >  - ask interesting questions
> >  - don't get distracted with shiny stuff  - working code first
> >  - http://wiki.laptop.org/go/User:Martinlanghoff
> >
>
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