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

[Anthony Liguori]

On 05/26/2010 03:43 AM, Kevin Wolf wrote:
> Am 26.05.2010 03:31, schrieb Anthony Liguori:
>    
> > On 05/25/2010 04:01 PM, Aurelien Jarno wrote:
> >      
> > > I really think this patch can be useful, in my own case when testing
> > > debian-installer (I already cache=writeback). In short all that is about
> > > developing and testing, as opposed to run a VM in production, can
> > > benefit about that. This was one of the original use case of QEMU before
> > > KVM arrived.
> > >
> > > Unless someone can convince me not to do it, I seriously considering
> > > applying this patch.
> > >
> > >        
> > There really needs to be an indication in the --help output of what the
> > ramifications of this option are, in the very least.  It should also be
> > removable via a ./configure option because no sane distribution should
> > enable this for end users.
> >      
> We know better what you stupid user want?

What percentage of qemu users do you think have actually read qemu-doc.texi?

It's not a stretch for someone to have heard that cache options can 
improve performance, and then see cache=volatile in the help output, try 
it, and then start using it because they observe a performance improvement.

That's not being stupid.  I think it's a reasonable expectation for a 
user to have that their data is safe.

Regards,

Anthony Liguori

>   There are valid use cases for
> this cache option, most notably installation.
>
> I could agree with requesting that the option should be called
> cache=unsafe (or even Alex' cache=destroys_your_image), but that should
> really be enough to tell everyone that his data is not safe with this
> option.
>
> Kevin
>