Re: io performance...

[Max Waterman <davidmaxwaterman+kernel@fastmail.co.uk>]

Jeff V. Merkey wrote:
> Max Waterman wrote:
>
> > Jeff V. Merkey wrote:
> >
> > > Max Waterman wrote:
> > >
> > > > One further question. I get these messages 'in' dmesg :
> > > >
> > > > sda: asking for cache data failed
> > > > sda: assuming drive cache: write through
> > > >
> > > > How can I force it to be 'write back'?
> > >
> > >
> > >
> > >
> > > Forcing write back is a very bad idea unless you have a battery 
> > > backed up RAID controller.  
> >
> >
> > We do.
> >
> > In any case, I wonder what the consequences of assuming 'write 
> > through' when the array is configured as 'write back'? Is it just 
> > different settings for different caches?
>
>
> It is.  This is something that should be configured in a RAID 
> controller.  OS should always be write through.

Ok, thanks for clearing that up, though I now wonder why the message is 
there.

<shrug>

Max.

> Jeff
>
> > Max.
> >
> > > Jeff
> > >
> > > > Max.
> > > > -
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