On Mon, Jan 16, 2017 at 10:52:08AM -0800, W Kern wrote: Libvirt has no default policy - it just delegates to whatever QEMU uses as the default. The current recommendation from the QEMU developers is that "native" is currently the best performing setting in most scenarios. The only time you should *not* use "native" is if you have *not* pre-allocated images. eg if you use sparse raw images, or have qcow2 images which did not have "preallocation" option given to "qemu-img create". For these you should use "threads". This is to avoid guest stalls when the host OS has to allocate a filesystem block to grow the file. Also note the io setting is only relevant for file/block device backed disks. ie if using the in-QEMU network client for RBD, Gluster, iSCSI, NFS, etc thenm the io setting has no effect at all so can be ignored. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|