Host Aggregate
A host aggregate is a group of hosts within your virtualized cluster that share common characteristics. Host aggregates are a mechanism to create specialized groupings of hosts that have specific properties, with the purpose of enabling provisioning of VMs that require those properties on those hosts.
You can create a host aggregate by navigating to the Private Cloud Director UI and selecting 'Infrastructure' -> 'Host Aggregates' from the left nav bar. When you create a new host aggregate, you get to specify a name for the aggregate and a set of key-value pairs that describe the specific properties of the hosts that will belong to this host aggregate.
For example, you may wish to create a group of hosts within your virtualized cluster that have Oracle licensing enabled on them. You can do this by creating an aggregate called "Oracle Hosts" and within that aggregate, creating a key-value pair with values "Oracle-License" and "True". You can then add the hosts that you know have Oracle license installed on them to this aggregate.
This will enable you to provision VMs that require Oracle licensing to place on these hosts. You will do this by first creating a flavor that references this host aggregate and then using that flavor to create your VM. Read about Flavors and Host Aggregates for how to do this.
Host Allocation Ratio
Allocation ratios determine how compute resources (CPU, memory, and disk) are over-committed on a host. The following default values are used for the initial allocation ratios for a new compute node:
- initial_cpu allocation_ratio: The initial virtual CPU (VCPU) inventory allocation ratio for a new compute node record. Defaults to 16.0, implying a 16:1 ratio of provisioned:available CPU (VCPU) inventory allocation. In other words, 16 times the number of available VCPUs are provisioned by default.
- initial_ram allocation_ratio: The initial memory inventory allocation ratio (in MB) for a new compute node record. Defaults to 1.5, implying a 1.5:1 ratio of provisioned:available memory inventory allocation. In other words, 1.5 times the amount of available memory is provisioned by default.
- initial_disk allocation_ratio: The initial disk inventory allocation ratio (in GB) for a new compute node record. Defaults to 1.0., implying a 1:1 ratio of provisioned:available disk inventory allocation. In other words, 1 times the amount of available memory is provisioned by default.
Configure Host Allocation Ratios
- Navigate to the "Infrastructure" menu in the Private Cloud Director UI.
- Select the "Host Aggregates" submenu.
- Select the host aggregate you intend to modify (assuming one has already been created).
- Click "Edit Host Aggregate".
- In the Host Aggregate Settings, select "Add Metadata".
- Specify the Key as cpu_allocation_ratio and the Value as the intended ratio, e.g. 4.0.
You can repeat the same steps for ram_allocation_ratio and disk_allocation_ratio if required.