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

[Aurelien Jarno <aurelien@aurel32.net>]

On Tue, May 25, 2010 at 08:31:20PM -0500, Anthony Liguori wrote:
> 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

That's indeed something than can be done, but to avoid double standards,
it should also be done for other features that can lead to data
corruption. I am talking for example on the qcow format, which is not
really supported anymore.

> also be removable via a ./configure option because no sane
> distribution should enable this for end users.
> 

I totally disagree. All the examples I have given apply to qemu *users*,
not qemu developers. They surely don't want to recompile qemu for their
usage. Note also that what is proposed in this patch was the default not
too long ago, and that a lot of users complained about the new default 
for their usage, they see it as a regression. We even had to put a note
explaining that in the Debian package to avoid to many bug reports. 
cache=writeback only answer partially to this use case.

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