The vRealize Operations Manager instance hosting the federation management pack should be sized just like any other vRealize Operations Manager instances.

For more information, see the KB article 2150421. The following are the best practices.
  • Out-of-the-box, vRealize Operations Federation Management Pack collects data for objects such as ESXi hosts, clusters, datacenters, datastores, and so on. Virtual machine data is not collected. Based on this, most of the environments can be monitored with one Extra Large Node.
  • The federation instance of vRealize Operations Manager should be used only for collecting data from the federation MP. No other MP on this vRealize Operations Manager instance should be configured to collect from any other data sources.
  • If you add new objects and metrics to an existing deployment of your federation vRealize Operations Manager instance, ensure to run the sizing calculator to meet the sizing requirements.
  • With vRealize Operations Federation Management Pack, you can either collect data directly from child vRealize Operations Manager instances or use a remote collector to optimize the collection process. The default collection cycle of vRealize Operations Federation Management Pack is 5 minutes. This time interval works accurately for a centralized vRealize Operations Manager collecting data from other child vRealize Operations Manager instances that are located within a short distance. You can also use a remote collector for data collection. Otherwise, when centralized vRealize Operations Manager collects data directly without a remote collector and latency is long, you can set the collection interval to 15 minutes. This ensures data collection without any gaps.
  • As most of the federation use cases are met by collecting data for objects other than virtual machines from your environment, it is recommended to avoid the collection of virtual machine data as this drastically increases the sizing requirement for the federation instance in a large-scale environment.