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

[Aurelien Jarno]

On Tue, May 25, 2010 at 07:59:18PM +0200, Alexander Graf wrote:
> Anthony Liguori wrote:
> > On 05/17/2010 11:23 AM, Paul Brook wrote:
> >>>> I don't see a difference between the results. Apparently the barrier
> >>>> option doesn't change a thing.
> >>>>        
> >>> Ok.  I don't like it, but I can see how it's compelling.  I'd like to
> >>> see the documentation improved though.  I also think a warning printed
> >>> on stdio about the safety of the option would be appropriate.
> >>>      
> >> I disagree with this last bit.
> >>
> >> Errors should be issued if the user did something wrong.
> >> Warnings should be issued if qemu did (or will soon do) something
> >> other than
> >> what the user requested, or otherwise made questionable decisions on the
> >> user's behalf.
> >>
> >> In this case we're doing exactly what the user requested. The only
> >> plausible
> >> failure case is where a user is blindly trying options that they
> >> clearly don't
> >> understand or read the documentation for. I have zero sympathy for
> >> complaints
> >> like "Someone on the Internet told me to use --breakme, and broke
> >> thinks".
> >>    
> >
> > I see it as the equivalent to the Taint bit in Linux.  I want to make
> > it clear to users up front that if you use this option, and you have
> > data loss issues, don't complain.
> >
> > Just putting something in qemu-doc.texi is not enough IMHO.  Few
> > people actually read it.
> 
> So what exactly is the conclusion here? I really want to see this
> getting merged
> 

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.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net