5 Questions about OpenStack Compute (Nova)

I'm studying for the Mirantis OpenStack Cloud Certification exam.  One of the ways I'm learning is to read through the official training material, making up my own questions along the way.

Today I'm starting with OpenStack Compute, also known as Nova:

1. How does the Compute use the nova-scheduler service?

  • Compute uses the nova-scheduler service to dispatch compute and volume requests.
  • For example, the nova-scheduler service determines which host a VM should launch on.  (Host means a physical node that has the nova-compute service running on it.)

2. How does nova-scheduler interact with other components?

  • The nova-scheduler interacts via the queue and central database repo.  The queue is the essential communications hub.

3. Where do compute nodes (hosts) publish their status, resources available, and hardware capabilities?

  • Compute nodes (hosts) publish their capabilities, status, and resources to nova-scheduler through the queue.  Nova-scheduler collects this data (in the nova database) and uses it to make decisions when a request comes in.

4. What default criteria must a host (compute node) meet for nova-scheduler to determine it is suitable for VM placement?
  • Must be in the requested availability zone (AvailabilityZoneFilter)
  • Must have sufficient RAM available (RamFilter)
  • Must be capable of servicing the request (ComputeFilter)

5. Which component supports filtering and weighting to make informed decisions on where a new instance should be created?
  • Filter Scheduler

More to come ...

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