Bug 1974241, clarified infra node sizing guidance

Author: ahardin-rh

modules/infrastructure-node-sizing.adoc

@@ -5,7 +5,7 @@
 [id="infrastructure-node-sizing_{context}"]
 =  Infrastructure node sizing
 
-The infrastructure node resource requirements depend on the cluster age, nodes, and objects in the cluster, as these factors can lead to an increase in the number of metrics or time series in Prometheus. The following infrastructure node size recommendations are based on the results of cluster maximums and control plane density focused testing.
+_Infrastructure nodes_ are nodes that are labeled to run pieces of the {product-title} environment. The infrastructure node resource requirements depend on the cluster age, nodes, and objects in the cluster, as these factors can lead to an increase in the number of metrics or time series in Prometheus. The following infrastructure node size recommendations are based on the results of cluster maximums and control plane density focused testing.
 
 [options="header",cols="3*"]
 |===
@@ -29,6 +29,8 @@ The infrastructure node resource requirements depend on the cluster age, nodes,
 
 |===
 
+In general, three infrastructure nodes are recommended per cluster.
+
 [IMPORTANT]
 ====
 These sizing recommendations are based on scale tests, which create a large number of objects across the cluster. These tests include reaching some of the cluster maximums. In the case of 250 and 500 node counts on a {product-title} {product-version} cluster, these maximums are 10000 namespaces with 61000 pods, 10000 deployments, 181000 secrets, 400 config maps, and so on. Prometheus is a highly memory intensive application; the resource usage depends on various factors including the number of nodes, objects, the Prometheus metrics scraping interval, metrics or time series, and the age of the cluster. The disk size also depends on the retention period. You must take these factors into consideration and size them accordingly.

scalability_and_performance/recommended-host-practices.adoc

@@ -38,3 +38,4 @@ include::modules/infrastructure-node-sizing.adoc[leveloffset=+1]
 
 * xref:../scalability_and_performance/planning-your-environment-according-to-object-maximums.adoc#planning-your-environment-according-to-object-maximums[{product-title}
 cluster maximums]
+* xref:../machine_management/creating-infrastructure-machinesets.adoc#creating-infrastructure-machinesets[Creating infrastructure machine sets]