I have written a patch to the libvirt_domain_disk_add function which does the following things: 1. Allow adding block devices as disks with libvirt_domain_disk_add 2. Removed the xflags parameter (not relevant as no xml is returned anyways) 3. Added the cache option to control cache mode (either default, none, writeback or writethrough) 4. Added the io option to control the used io mode (either default, native or threads) Besides this, I have rewritten it so it now uses the virDomainAttachDevice function, which is meant for these things, instead of pasting the device XML by hand into the domain XML. I have uploaded this to my github clone at https://github.com/martijnotto/libvirt-php It would be nice if this could be included in a future release of lbvirt-php. If the code does not meet a coding standard for libvirt-php or if there is some other concern, please let me know and I will do what I can to improve it. With Regards, Martijn Otto Copernica B.V.