Re: raid is dangerous but that's secret (was Re: [patch] ext2/3:document conditions when reliable operation is possible)

[Ric Wheeler]

On 08/27/2009 06:13 PM, Pavel Machek wrote:
> > > > Repeat experiment until you get up to something like google scale or the
> > > > other papers on failures in national labs in the US and then we can have an
> > > > informed discussion.
> > > On google scale anvil lightning can fry your machine out of a clear sky.
> > >
> > > However, there are still a few non-enterprise users out there, and knowing
> > > that specific usage patterns don't behave like they expect might be useful to
> > > them.
> >
> > You are missing the broader point of both papers. They (and people like
> > me when back at EMC) look at large numbers of machines and try to fix
> > what actually breaks when run in the real world and causes data loss.
> > The motherboards, S-ATA controllers, disk types are the same class of
> > parts that I have in my desktop box today.
> ...
> > These errors happen extremely commonly and are what RAID deals with well.
> >
> > What does not happen commonly is that during the RAID rebuild (kicked
> > off only after a drive is kicked out), you push the power button or have
> > a second failure (power outage).
> >
> > We will have more users loose data if they decide to use ext2 instead of
> > ext3 and use only single disk storage.
>
> So your argument basically is
>
> 'our abs brakes are broken, but lets not tell anyone; our car is still
> safer than a horse'.
>
> and
>
> 'while we know our abs brakes are broken, they are not major factor in
> accidents, so lets not tell anyone'.
>
> Sorry, but I'd expect slightly higher moral standards. If we can
> document it in a way that's non-scary, and does not push people to
> single disks (horses), please go ahead; but you have to mention that
> md raid breaks journalling assumptions (our abs brakes really are
> broken).
> 								Pavel


You continue to ignore the technical facts that everyone (both MD and ext3) 
people put in front of you.

If you have a specific bug in MD code, please propose a patch.

Ric

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