Upgrading from Juno to Kilo: Overview

Note that the following holds true for all of the described upgrade scenarios:

All scenarios involve some service interruptions.
Running instances will not be affected by the upgrade process unless you (a) reboot a compute node or (b) explicitly shut down an instance.

Scenario 1: All at once

In this scenario, you will take down all of your OpenStack services at the same time, and will not bring them back up until the upgrade process is complete.

Pros: This process is very simple. Because everything is down there is no orchestration involved.

Cons: All of your services are unavailable all at once. In a large environment, this can result in a potentially extensive downtime as you wait for database schema upgrades to complete.

Read about this scenario in Upgrade Scenario 1.

Scenario 2: Service-by-service with live compute upgrade

In this scenaior, you upgrade one service at a time. You perform rolling upgrades of your compute hosts, taking advantage of the fact that nova-compute from Juno can communicate with a Kilo control plane.

Pros: This process minimizes the downtime to your existing compute workloads.

This is our recommended upgrade procedure for most environments.

Cons: This is a more complex procedure, and mistakes or undiscovered compatibility issues can unexpectedly turn it into Scenario 1.

Read about this scenario in Upgrade Scenario 2 (HA) if you are running an HA environment, or Upgrade Scenaior 2 (non-HA) if you are running in a non-HA environment.