Apply the attached patch on top of yours which contains miscellaneous fixes. If you use ‘./configure --enable-gcc-warnings’ then it will enable GCC warnings. The test doesn't really test anything. If extents are being cached then I have two ideas about how you could see that: Either (1) you could look at debug messages, the second extents call shouldn't be processed at the plugin layer. Or (2) write a small nbdkit-sh-plugin script which should see the first extent request and not the second one (and even test that a subsequent write should kill the cache so another extent request is seen by the plugin). Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/