Use the Dynamic Resource Balancer service

Available since MOSK 24.2 TechPreview

The Dynamic Resource Balancer (DRB) service automatically moves OpenStack instances around to achieve more optimal resource usage in a MOSK cluster.

Consult your cloud administrator to determine if this service is enabled in your cloud and which mode is used. The DRB service relies on the OpenStack live migration mechanism to ensure that instances can be seamlessly moved to another hypervisor of its choice.

Note

The live migration mode supports local block storage. The live migration mechanism automatically determines whether Nova should migrate using a local block storage or a shared storage.

Depending on the nature of your workload and configuration of the MOSK cluster, you can explicitly configure the DRB service in two ways:

  • Opt out of automatic instance migration if your instances are sensitive to live migration. For example, if the instances rely on special local resources such as SR-IOV-based virtual NICs or cannot tolerate CPU throttling.

  • Opt in to optimize your instance placement at any time. In this case, if the DRB service is configured not to move instances by default, this allows your applications to relocate away from noisy neighbors that are consuming excessive shared resources on a hypervisor.

Prohibit DRB from migrating an instance

If the DRB service in your MOSK cluster is configured to auto-migrate all instances by default, you, as the owner of the instance, can opt out of such automated migrations.

To achieve this, tag your instances with lcm.mirantis.com:no-drb. For example, using the openstack CLI:

openstack --os-compute-api-version 2.26 server set <server-name-or-id> \
    --tag lcm.mirantis.com:no-drb

Successfull execution of the command above produces no output. To revert to the default behavior, use the openstack server unset command in a similar way.

Note

OpenStack instance tags are distinct from metadata (key-value pairs). Therefore, use instance tagging explicitly for this purpose.

Allow DRB to migrate an instance at any time

If the DRB service in your {{ product_name_abbr}} cloud is configured to move only specific instances, in order for the placement of your instances to get automatically optimized, you need to explicitly tag each instance with lcm.mirantis.com:drb. For example, using the openstack CLI:

openstack --os-compute-api-version 2.26 server set <server-name-or-id> \
    --tag lcm.mirantis.com:drb

Successfull execution of the command above produces no output. To revert to the default behavior, use the openstack server unset command in a similar way.

Note

OpenStack instance tags are distinct from metadata (key-value pairs). Therefore, use instance tagging explicitly for this purpose.