[Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive

[Anthony Liguori]

On 05/17/2010 08:17 AM, Alexander Graf wrote:
> On 17.05.2010, at 15:09, Anthony Liguori wrote:
>
>    
> > On 05/17/2010 08:02 AM, Alexander Graf wrote:
> >      
> > > > My concern is that ext3 exaggerates the cost of fsync() which will result in 
> > > > diminishing value over time for this feature as people move to ext4/btrfs.
> > > >
> > > >          
> > > There will be ext3 file systems for years out. Just because people can use 
> > > better and faster file systems doesn't mean they do. And I'm sure they can't 
> > > always choose. If anything, I can try and see what the numbers look like for 
> > > xfs.
> > >
> > >        
> > But ext3 with barrier=1 is pretty uncommon in practice.  Another data point 
> > would be an ext3 host file system with barrier=0.
> >      
> Who defines what is common and what not? To me, the SLES11 default is common. 
> In fact, the numbers in the referred mail were done on an 11.1 system.
>    

But it wasn't the SLES10 default so there's a smaller window of systems 
that are going to be configured this way.  But this is orthogonal to the 
main point.  Let's quantify how important this detail is before we 
discuss the affected user base.

Regards,

Anthony Liguori

> Alex
>
>