On 05/31/2017 01:31 AM, Zhenguo Niu wrote:
On Wed, May 31, 2017 at 12:20 PM, Ed Leafe <[email protected]
<mailto:[email protected]>> wrote:
On May 30, 2017, at 9:36 PM, Zhenguo Niu <[email protected]
<mailto:[email protected]>> wrote:
> as placement is not splitted out from nova now, and there would be users
who only want a baremetal cloud, so we don't add resources to placement yet, but
it's easy for us to turn to placement to match the node type with mogan flavors.
Placement is a separate service, independent of Nova. It tracks
Ironic nodes as individual resources, not as a "pretend" VM. The
Nova integration for selecting an Ironic node as a resource is still
being developed, as we need to update our view of the mess that is
"flavors", but the goal is to have a single flavor for each Ironic
machine type, rather than the current state of flavors pretending
that an Ironic node is a VM with certain RAM/CPU/disk quantities.
Yes, I understand the current efforts of improving the baremetal nodes
scheduling. It's not conflict with mogan's goal, and when it is done, we
can share the same scheduling strategy with placement :)
Mogan is a service for a specific group of users who really want a
baremetal resource instead of a generic compute resource, on API side,
we can expose RAID, advanced partitions, nics bonding, firmware
management, and other baremetal specific capabilities to users. And
unlike nova's host based availability zone, host aggregates, server
groups (ironic nodes share the same host), mogan can make it possible to
divide baremetal nodes into such groups, and make Rack aware for
affinity and anti-affinity when scheduling.
Zhenguo Niu brings up a very good point here. Currently, all Ironic
nodes are associated with a single host aggregate in Nova, because of
the vestigial notion that a compute *service* (ala the nova-compute
worker) was equal to the compute *node*.
In the placement API, of course, there's no such coupling. A placement
aggregate != a Nova host aggregate.
So, technically Ironic (or Mogan) can call the placement service to
create aggregates that match *its* definition of what an aggregate is
(rack, row, cage, zone, DC, whatever). Furthermore, Ironic (or Mogan)
can associate Ironic baremetal nodes to one or more of those placement
aggregates to get around Nova host aggregate to compute service coupling.
That said, there's still lots of missing pieces before placement gets
affinity/anti-affinity support...
Best,
-jay
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