Overhaul README
The README of this important charm is in dire need of an overhaul. Depends-On: I1dafd2a87c4195e9d52f3f4840a5efa423c895d0 Change-Id: I29538070d9370b3e7bafd5ff13ad8a476652b643
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Peter Matulis
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README.md
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README.md
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# Overview
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This charm provides Nova Compute, the OpenStack compute service. Its target
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platform is Ubuntu (preferably LTS) + OpenStack.
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The nova-compute charm deploys [Nova Compute][upstream-compute], the core
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OpenStack service that provisions virtual instances (VMs) and baremetal servers
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(via [Ironic][cdg-ironic]). The charm works alongside other Juju-deployed
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OpenStack services.
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# Usage
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The following interfaces are provided:
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- cloud-compute - Used to relate (at least) with one or more of
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nova-cloud-controller, glance, ceph, cinder, mysql, ceilometer-agent,
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rabbitmq-server, neutron
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- nrpe-external-master - Used to generate Nagios checks.
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## Configuration
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This section covers common and/or important configuration options. See file
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@ -20,18 +14,56 @@ This section covers common and/or important configuration options. See file
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default values. See the [Juju documentation][juju-docs-config-apps] for details
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on configuring applications.
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#### `config-flags`
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A comma-separated list of key=value configuration flags. These values will be
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placed in the [DEFAULT] section of the `nova.conf` file.
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#### `enable-live-migration`
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Allows the live migration of VMs.
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#### `enable-resize`
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Allows the resizing of VMs.
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#### `migration-auth-type`
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Selects the TCP authentication scheme to use for live migration. The only
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accepted value is 'ssh'.
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#### `customize-failure-domain`
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When MAAS is the backing cloud and this option is set to 'true' then all
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MAAS-defined zones will become available as Nova availability zones, and option
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`default-availability-zone` will be overridden. See section [Availability
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Zones][anchor-az].
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#### `default-availability-zone`
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Sets a single default Nova availability zone. It is used when a VM is created
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without a Nova AZ being specified. The default value is 'nova'. A non-default
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Nova AZ must be created manually (i.e. `openstack aggregate create`). See
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section [Availability Zones][anchor-az].
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#### `libvirt-image-backend`
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Specifies what image backend to use. Possible values are 'rbd', 'qcow2',
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'raw', and 'flat'. The default behaviour is for Nova to use qcow2.
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#### `openstack-origin`
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The `openstack-origin` option states the software sources. A common value is an
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OpenStack UCA release (e.g. 'cloud:xenial-queens' or 'cloud:bionic-ussuri').
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See [Ubuntu Cloud Archive][wiki-uca]. The underlying host's existing apt
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sources will be used if this option is not specified (this behaviour can be
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explicitly chosen by using the value of 'distro').
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States the software sources. A common value is an OpenStack UCA release (e.g.
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'cloud:bionic-train' or 'cloud:focal-wallaby'). See [Ubuntu Cloud
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Archive][wiki-uca]. The underlying host's existing apt sources will be used if
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this option is not specified (this behaviour can be explicitly chosen by using
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the value of 'distro').
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#### `pool-type`
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The `pool-type` option dictates the Ceph storage pool type. See sections 'Ceph
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pool type' and 'RBD Nova images' for more information.
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Dictates the Ceph storage pool type. See sections [Ceph pool
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type][anchor-ceph-pool-type] and [RBD Nova images][anchor-rbd-nova-images] for
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more information.
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## Ceph pool type
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@ -97,69 +129,94 @@ the compression behaviour.
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> **Note**: BlueStore compression is supported starting with Ceph Mimic.
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## Database
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## Deployment
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Nova compute only requires database access if using nova-network. If using
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Neutron, no direct database access is required and the shared-db relation need
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not be added. The nova-network feature is not available in Ussuri and later,
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and so this interface produces a warning if added.
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These deployment instructions assume that the following applications are
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present: glance, nova-cloud-controller, ovn-chassis, and rabbitmq-server.
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Storage backends used for VM disks and volumes are configured separately (see
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sections [Ceph backed storage][anchor-ceph-backed-storage] and [Local Cinder
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storage][anchor-local-cinder-storage].
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## Networking
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Let file `nova-compute.yaml` contain the deployment configuration:
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This charm support nova-network (legacy) and Neutron networking.
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```yaml
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nova-compute:
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config-flags: default_ephemeral_format=ext4
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enable-live-migration: true
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enable-resize: true
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migration-auth-type: ssh
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openstack-origin: cloud:focal-wallaby
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```
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## Ceph backed storage
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To deploy nova-compute to machine '5':
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This charm supports a number of different storage backends depending on
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your hypervisor type and storage relations.
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juju deploy --to 5 --config nova-compute.yaml nova-compute
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juju add-relation nova-compute:image-service glance:image-service
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juju add-relation nova-compute:cloud-compute nova-cloud-controller:cloud-compute
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juju add-relation nova-compute:neutron-plugin ovn-chassis:nova-compute
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juju add-relation nova-compute:amqp rabbitmq-server:amqp
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### RBD Nova images
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### Ceph backed storage
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To make Ceph the storage backend for Nova non-bootable disk images
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configuration option `libvirt-image-backend` must be set to 'rbd'. The below
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relation is also required:
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Two concurrent Ceph backends are supported: RBD Nova images and RBD Cinder
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volumes. Each backend uses its own set of cephx credentials.
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The steps below assume a pre-existing Ceph cluster (see the
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[ceph-mon][ceph-mon-charm] and [ceph-osd][ceph-osd-charm] charms).
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#### RBD Nova images
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RBD Nova images are enabled by setting option `libvirt-image-backend` to 'rbd'
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and by adding a relation to the Ceph cluster:
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juju config nova-compute libvirt-image-backend=rbd
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juju add-relation nova-compute:ceph ceph-mon:client
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### RBD Cinder volumes
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> **Warning**: Changing the value of option `libvirt-image-backend` will orphan
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any disks that were set up under a different setting. This will cause the
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restarting of associated VMs to fail.
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Starting with OpenStack Ocata, in order to maintain Cinder RBD support the
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below relation is required:
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This solution will place both root and ephemeral disks in Ceph.
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> **Pro tip**: An alternative is to selectively store just root disks in Ceph
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by using Cinder as an intermediary. See section [RBD Cinder
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volumes][anchor-rbd-cinder] as well as [Launch an instance from a
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volume][upstream-volume-boot] in the Nova documentation.
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#### RBD Cinder volumes
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RBD Cinder volumes are enabled by adding a relation to Cinder via the
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cinder-ceph application. Assuming Cinder is already backed by Ceph (see the
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[cinder-ceph][cinder-ceph-charm] charm):
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juju add-relation nova-compute:ceph-access cinder-ceph:ceph-access
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This allows Nova to communicate with multiple Ceph backends using different
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cephx keys and user names.
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> **Note**: The `nova-compute:ceph-access` relation is not needed for OpenStack
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releases older than Ocata.
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### Local Cinder storage
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To use local storage, Cinder will need to be configured to use local block
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devices. See the [cinder][cinder-charm] charm for details.
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## Availability Zones
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There are two options to provide default_availability_zone config
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for nova nodes:
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Nova AZs can be matched with MAAS zones depending on how options
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`default-availability-zone` and `customize-failure-domain` are configured. See
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[Availability Zones][cdg-ha-az] in the [OpenStack Charms Deployment Guide][cdg]
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for in-depth coverage of how this works.
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- default-availability-zone
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- customize-failure-domain
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## SSH keys and VM migration
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The order of precedence is as follows:
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VM migration requires the sharing of public SSH keys (host and several select
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users) among the compute hosts. By design, only those hosts belonging to the
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same application group will get each other's keys. This means that VM migration
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cannot occur (without manual intervention) between hosts belonging to different
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groups.
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1. Information from a Juju provider (JUJU_AVAILABILITY_ZONE)
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if customize-failure-domain is set to True and Juju
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has set the JUJU_AVAILABILITY_ZONE to a non-empty value;
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2. The value of default-availability-zone will be used
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if customize-failure-domain is set to True but no
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JUJU_AVAILABILITY_ZONE is provided via hook
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context by the Juju provider;
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3. Otherwise, the value of default-availability-zone
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charm option will be used.
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The default_availability_zone in Nova affects scheduling if a
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given Nova node was not placed into an aggregate with an
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availability zone present as a property by an operator. Using
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customize-failure-domain is recommended as it provides AZ-aware
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scheduling out of the box if an operator specifies an AZ during
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instance creation.
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These options also affect the AZ propagated down to networking
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subordinates which is useful for AZ-aware Neutron agent scheduling.
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> **Note:** The policy of only sharing SSH keys amongst hosts of the same
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application group may be struck down. This is being tracked in bug [LP
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#1468871][lp-bug-1468871].
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## NFV support
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@ -190,12 +247,12 @@ In addition this charm declares two extra-bindings:
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Note that the nova-cloud-controller application must have bindings to the same
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network spaces used for both 'internal' and 'migration' extra bindings.
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## Scaling down
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## Scaling back
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Scaling down the nova-compute application implies the removal of one or more
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Scaling back the nova-compute application implies the removal of one or more
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compute nodes. This is documented as a cloud operation in the [OpenStack Charms
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Deployment Guide][cdg]. See [Scaling down the nova-compute
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application][cdg-ops-scale-down-nova-compute].
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Deployment Guide][cdg]. See [Remove a Compute
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node][cdg-ops-scale-in-nova-compute].
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## Actions
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@ -242,5 +299,20 @@ Please report bugs on [Launchpad][lp-bugs-charm-nova-compute].
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[wiki-uca]: https://wiki.ubuntu.com/OpenStack/CloudArchive
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[cdg-ceph-erasure-coding]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-erasure-coding.html
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[ceph-bluestore-compression]: https://docs.ceph.com/en/latest/rados/configuration/bluestore-config-ref/#inline-compression
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[cdg-ops-scale-down-nova-compute]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/ops-scale-down-nova-compute.html
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[cdg-ops-scale-in-nova-compute]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/ops-scale-in-nova-compute.html
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[cdg-nfv]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/nfv.html
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[cdg-ironic]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/ironic.html
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[cinder-charm]: https://jaas.ai/cinder
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[cinder-ceph-charm]: https://jaas.ai/cinder-ceph
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[ceph-mon-charm]: https://jaas.ai/ceph-mon
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[ceph-osd-charm]: https://jaas.ai/ceph-osd
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[upstream-compute]: https://docs.openstack.org/nova/
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[cdg-ha-az]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-ha.html#availability-zones
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[anchor-az]: #availability-zones
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[anchor-ceph-pool-type]: #ceph-pool-type
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[anchor-ceph-backed-storage]: #ceph-backed-storage
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[anchor-local-cinder-storage]: #local-cinder-storage
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[anchor-rbd-nova-images]: #rbd-nova-images
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[anchor-rbd-cinder]: #rbd-cinder-volumes
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[upstream-volume-boot]: https://docs.openstack.org/nova/latest/user/launch-instance-from-volume.html
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[lp-bug-1468871]: https://bugs.launchpad.net/charms/+source/nova-cloud-controller/+bug/1468871
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