Another problem is that the blktapctrl daemon itself does not even start if the "xenblktap" kernel module is not loaded. (blktapctrl is started automatically by xend.) So to use tap:aio with Xen from Debian lenny you need to - create a symlink named "tapdisk" pointing to /usr/lib/xen-3.2-1/bin/tapdisk somewhere in root's $PATH and - load the "xenblktap" kernel module before xend is started (e.g. using /etc/modules). http://lists.alioth.debian.org/pipermail/pkg-xen-devel/2009-June/002344.html