*** /home/onboard/files *** directory layout.

This directory should contain CD/DVD and VM images, and is the "root"
browsed by jQueryFileTree popup window.

/home/onboard/files/ISO

/home/onboard/files/QEMU

There's a special subdir:

/home/onboard/files/[network] 

which contains mount points for networked filesystems which might be later 
"optimized" as in the following examples.

IT IS YOUR CARE to ensure thet distributed / networked filesystems are actually
mounted there, otherwise you will end up creating vm images on local storage. 
(Until an OnBoard module is created to manage GlusterFS and such).

Suppose you open/pick 

[network]/gluster/localhost/gv0/QEMU/MyVM/disk0.qcow2 .

Well, /home/onboard/files/[network]/gluster/localhost/gv0 is the mount point
for a GlusterFS volume. The volume is mounted (via FUSE) just for the sake of 
browsing, and to allow an easier access for qemu-img.

Actually, QEMU is now able to bypass FUSE to improve performance [1].

The idea, within our code,  is to automatically translate a file path under the 
special directory '[network]' into a "direct" URI. So the above file path get 
translated into:

file=gluster://localhost/gv0/QEMU/MyVM/disk0.qcow2 

in qemu-system-x86_64 -drive command line option.

This should be true for other distributed storage systems - for possible 
future developments.

To have GlusterFS/QEMU integration you need QEMU >= 1.3 (compiled with Gluster suport) 
and GlusterFS >= 3.4 (which provides libgfapi).

** A NOTE ON qemu-img **

When the cluster is in under-optimal state (i.e. a replica brick or peer is 
unavailable) qemu-img gluster:// is VERY slow: so it's better to make it work
on FUSE mount points rather than on gluster:// URLs, which should be used by
qemu only.

--

[1] http://raobharata.wordpress.com/2012/10/29/qemu-glusterfs-native-integration/