Starting with GlusterFS 3.4.0 there is a an API which can be used to access files on a GlusterFS volume directly without the FUSE-mount. Qemu supports this starting from version 1.2.0.

The XML has to be changed only slightly. Following is an example:

    <disk type='network' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source protocol='gluster' name='virtualization/vm-templates/5b77d2f6-061f-410c-8ee7-9e61da6f1927/f3d87cf9-f7d8-4224-b908-cc9fc6c8fcd4.qcow2'>
        <host name='10.1.120.11'/>
      </source>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </disk>

What changes:

disk-type

has to be network instead of file

source

has now a protocol and a name instead of a file attribute as well as a new subelement host, where the name is the filename without /var/