On Wed, Jan 08, 2014 at 11:11:35PM +0100, Paolo Bonzini wrote: > Is guestfish using "discard=on"?
No. Adding the discard=on parameter does indeed fix this: 13M /tmp/test1 17M /tmp/test2 However why isn't this the default? Is there a case where discard=on would be undesirable? It's extremely difficult to know when it's safe to add this parameter. Qemu gives no indication of when using discard=.. is safe (ie. won't cause qemu to fail to start up or fail in some other way). It's even worse when we have to go via libvirt which itself doesn't expose qemu's capabilities upwards. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW
