Am Donnerstag 29 März 2007 schrieb David Chinner:
> On Thu, Mar 29, 2007 at 04:56:21PM +0200, Martin Steigerwald wrote:
> > Am Montag 26 März 2007 schrieb David Chinner:
> > > > Is there some mount flag to say "cope without barriers" or
> > > > "require barriers" ??
> > >
> > > XFs has "-o nobarrier" to say don't use barriers, and this is
> > > *not* the default. If barriers don't work, we drop back to "-o
> > > nobarrier" after leaving a loud warning inthe log....
> > Hello David!
> > Just a thought, maybe it shouldn't do that automatically, but require
> > the sysadmin to explicitely state "-o nobarrier" in that case.
> And prevent most existing XFS filesystems from mounting after
> a kernel upgrade? Think about the problems that might cause
> with XFs root filesystems on hardware/software that doesn't
> support barriers....
Granted. So it might turn out to be a decision between does not boot or is
not totally safe in power outages or crashes. I see no easy default
answer to that.
So while probably being a layering violation at least trying to disable
the write cache on devices without cache flush support unless "-o
nobarrier" (as in "I know what I am doing") is given, might help safety.
But this adds complexity and a possible source for bugs. And maybe trying
to disable write cache isn't safe on all setups?
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
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