On Tue, 25 Aug 2009 11:46:08 pm Christoph Hellwig wrote: > On Tue, Aug 25, 2009 at 11:41:37PM +0930, Rusty Russell wrote: > > On Fri, 21 Aug 2009 06:26:16 am Christoph Hellwig wrote: > > > Currently virtio-blk doesn't set any QUEUE_ORDERED_ flag by default, which > > > means it does not allow filesystems to use barriers. But the typical use > > > case for virtio-blk is to use a backed that uses synchronous I/O > > > > Really? Does qemu open with O_SYNC? > > > > I'm definitely no block expert, but this seems strange... > > Rusty. > > Qemu can open it various ways, but the only one that is fully safe > is O_SYNC (cache=writethrough). (Rusty goes away and reads the qemu man page). By default, if no explicit caching is specified for a qcow2 disk image, cache=writeback will be used. Are you claiming qcow2 is unusual? I can believe snapshot is less common, though I use it all the time. You'd normally have to add a feature for something like this. I don't think this is different. Sorry, Rusty. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
