Post #1894136

@vegard I'd want to check that you're comparing the same caching and writeback settings and ordering semantics; in some of the more careful modes I know the qemu code is careful not to tell the guest a write is complete until it gets to.. the os? the disk? not sure - but that can be a source of some perf differences. Still if it's actually 10% faster, then finding out why would be interesting and telling @stefanha !