Node Aggregates

Node Aggregates

Node aggregates, like nova’s host aggregates for VMs, can be regarded as a mechanism to further partition an availability zone; while availability zones are visible to users, node aggregates are only visible to administrators. Allow administrators to assign key-value pairs to groups of bare metal nodes. Each node can have multiple aggregates, each aggregate can have multiple key-value pairs, and the same key-value pair can be assigned to multiple aggregates. This information can be used in the scheduler to enable advanced scheduling by setting key-value pairs to flavor resource aggregates field.

Admin users can use the openstack baremetalcompute aggregate command to create, delete and manage aggregates. To see information for this command, run:

$ openstack baremetalcompute aggregate [TAB]
add        create     delete     list       list_node  remove     set        show       unset

Availability Zones (AZs)

Like Nova, the availability zone is actually a specific metadata attached to an aggregate. Adding that specific metadata to an aggregate makes the aggregate visible from an end-user perspective and consequently allows to schedule upon a specific set of nodes (the ones belonging to the aggregate).


One node can be in multiple aggregates, but it can only be in one availability zone

Affinity Zones

The affinity zone is also a specific metadata attached to an aggregate, which makes server group affinity and anti-affinity happen. You may define it as failure domains(e.g., by power circuit, rack, room, etc).


One node can be in multiple aggregates, but it can only be in one affinity zone

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