[openstack-dev] [nova] Moving storage placement out of the driver

Matthew Booth mbooth at redhat.com
Tue Nov 1 14:41:52 UTC 2016

For context, this is a speculative: should we, shouldn't we?

The VMware driver currently allows the user to specify what storage their
instance will use, I believe using a flavor extra-spec. We've also got
significant interest in adding the same to the libvirt driver, but we've
got some additional plumbing work to do first to allow us to persist this
metadata per-instance, independent of the host configuration. It was my
intention to add this logic to the libvirt driver along similar lines.

At the same time, we're adding resource providers. It's my layman's
understanding that a storage pool (in the abstract, not referring to a
particular implementation) will be modelled as a resource provider. A host
can, theoretically at least, have arbitrarily many of these, and one may be
attached to multiple hosts.

As it stands today, ComputeManager specifies what disks an instance should
have, and how large they should be. Where to put them is down to the
driver. If we're modelling this outside the driver and at least 2 drivers
are implementing it, I wonder if we shouldn't be implementing storage
policy at a higher level than the driver.


Matthew Booth
Red Hat Engineering, Virtualisation Team

Phone: +442070094448 (UK)
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