[openstack-dev] [nova] (Live migration track) Libvirt storage pools initial step

Matthew Booth mbooth at redhat.com
Thu Dec 17 19:14:20 UTC 2015

I'm off now for the holiday period, so I'm sharing what I'm sitting on.
This represents a bit over a week of staring at code, and a couple of days
of actual keyboard banging. It doesn't run. Details are in the commit
message, including where I think I'm going with this. Read the commit
message like a slightly more detailed spec.


I have a reasonable idea of where I want to go with this, but finding a
consumable set of steps to get there is challenging. The current code makes
lots of assumptions about storage in lots of places. Consequently, adding
to it without regressing is becoming increasingly difficult. Making the
wholesale change to libvirt storage pools, supporting multiple layouts in
the transition period, would require updating these assumptions everywhere
they exist in the code. My initial goal is to centralise these assumptions
whilst making minimal/no functional changes. Once all the code which
assumes on-disk layout is in one place, we can be more confident in making
changes to it, and more easily validate it. We can also more easily see
what the current assumptions are. This will also make it easier for people
to continue adding storage-related features to the libvirt driver.

Matthew Booth
Red Hat Engineering, Virtualisation Team

Phone: +442070094448 (UK)
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