Hy
i've being runnig D3 over an XEN machine... with CentOs with VM servers... an few hints i can give is about the disks ... make at least 3 storage,
1 for SO ( just the minium disk space)
1 for userdata and backup ( it depends how big your d3 data is, and how users use the linux server)
1 for D3 data
with that structure... if your SO crashes... you can create only a new disk for SO, and atached the other 2 disks
and when i see i had an stable env, i stop the d3 vm machine, shutdown the VM detache the userdata disk and d3data and take an snapshot only from the first disk, then i reattached the others disks and start all the service... with that in case some crash or so update error.. you have fast recovery