Hi, In some mail which was sent to someone else, you wrote: file: uses dom0 kernel page cache, and thus might give better performance than phy: or tap:aio:, but it''s also more insecure because of the caching. tap:aio: uses direct IO, so it bypasses dom0 kernel caches, and works like phy: in that sense. Thus here I come to refer to you.I have two questions: 1.What is difference between tap:qcow2 and tap2:tapdisk:qcow2? 2.Does tap:qcow2: and tap2:tapdisk:qcow2 use direct IO and bypass dom0 kernel caches? 3.If a qcow2 format image is based on a raw format image and this qcow2 format image is configured with "tap:qcow2" or "tap2:tapdisk:qcow2" , Does the VM created by this qcow2 format image use direct IO and bypass dom0 kernel caches? Thank you for any response~ hxk _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel