Re: [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes

[Anthony Liguori]

On 09/20/2010 10:08 AM, Kevin Wolf wrote:
> > If you're comfortable with a writeback cache for metadata, then you
> > should also be comfortable with a writeback cache for data in which
> > case, cache=writeback is the answer.
> >      
> Well, there is a difference: We don't pollute the host page cache with
> guest data and we don't get a virtual "disk cache" as big as the host
> RAM, but only a very limited queue of metadata.
>    

Would it be a mortal sin to open the file twice and have a cache=none 
version for data and cache=writeback for metadata?

The two definitely aren't consistent with each other but I think the 
whole point here is that we don't care.

It opens up some other possibilities too like cache=none for data and 
cache=writethrough for metadata which may be a useful combination.

Regards,

Anthony Liguori