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

[Paolo Bonzini]

On 05/26/2010 03:48 PM, Anthony Liguori wrote:
> We might get 100 bug reports about this "regression" but they concern
> much less than 1 bug report of image corruption because of power
> failure/host crash. A reputation of being unsafe is very difficult to
> get rid of and is something that I hear concerns about frequently.

True, but how many people will use cache=volatile?  Nobody is going to 
make it the default.  If a blog post appears "hey look cache=volatile 
will speedup your virtual machine", and gets so much momentum that 
people start using it and lose data because of it (which is highly 
hypothetical and unlikely), QEMU developers are not the ones to be blamed.

> I'm not suggesting that the compile option should be disabled by default
> upstream. But the option should be there for distributions because I
> hope that any enterprise distro disables it.

Actually it's perfectly possible that they will _enable_ it if a 
configure option is required to enable cache=volatile.  RHEL for example 
doesn't support at all running qemu directly, only via libvirt.  If 
libvirt doesn't pass cache=volatile to qemu, they're safe.

(Well, virt-install uses libvirt, so it couldn't use cache=volatile 
either, so I admit it's not a great example).

Paolo