Upstream RFC to QEMU: https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg04904.html

QEMU Bug 1265869


from the RFC:

This patch adds support for a new block device type called "vxhs".
Source code for the library that this code loads can be downloaded from:
https://github.com/MittalAshish/libqnio.git

Sample command line using JSON syntax:
./qemu-system-x86_64 -name instance-00000008 -S -vnc 0.0.0.0:0 -k en-us -vga 
cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -msg 
timestamp=on 
'json:{"driver":"vxhs","vdisk_id":"{c3e9095a-a5ee-4dce-afeb-2a59fb387410}","server":[{"host":"172.172.17.4","port":"9999"},{"host":"172.172.17.2","port":"9999"}]}'

Sample command line using URI syntax:
qemu-img convert -f raw -O raw -n 
/var/lib/nova/instances/_base/0c5eacd5ebea5ed914b6a3e7b18f1ce734c386ad 
vxhs://192.168.0.1:9999/%7Bc6718f6b-0401-441d-a8c3-1f0064d75ee0%7D