// Module included in the following assemblies:
//
// * osd_planning/osd-limits-scalability.adoc
// * rosa_planning/rosa-limits-scalability.adoc

:_mod-docs-content-type: REFERENCE
[id="control-plane-and-infra-node-sizing-and-scaling-sd_{context}"]
= Control plane and infrastructure node sizing and scaling

[role="_abstract"]
When you install
ifdef::openshift-rosa[]
a {product-title}
endif::[]
ifdef::openshift-dedicated[]
an {product-title}
endif::[]
cluster, the sizing of the control plane and infrastructure nodes are automatically determined by the compute node count. To maintain cluster stability, the Red{nbsp}Hat Site Reliability Engineering (SRE) team automatically adjusts your control plane and infrastructure nodes whenever you change your compute node count.

[id="node-sizing-during-installation_{context}"]
== Node sizing during installation

During the installation process, the sizing of the control plane and infrastructure nodes are dynamically calculated. The sizing calculation is based on the number of compute nodes in a cluster.

The following
ifdef::openshift-rosa[]
table lists
endif::[]
ifdef::openshift-dedicated[]
tables list
endif::[]
the control plane and infrastructure node sizing that is applied during installation.

ifdef::openshift-dedicated[]
AWS control plane and infrastructure node size:
endif::[]
[options="header",cols="3*"]
|===
|Number of compute nodes |Control plane size |Infrastructure node size

|1 to 25
|m5.2xlarge
|r5.xlarge

|26 to 100
|m5.4xlarge
|r5.2xlarge

|101 to 249
|m5.8xlarge
|r5.4xlarge
|===

ifdef::openshift-dedicated[]

{gcp-short} control plane and infrastructure node size:
[options="header",cols="2a,2a,2a"]
|===
|Number of compute nodes
|Control plane size
|Infrastructure node size

|1 to 25
|custom-8-32768
|custom-4-32768-ext

|26 to 100
|custom-16-65536
|custom-8-65536-ext

|101 to 249
|custom-32-131072
|custom-16-131072-ext
|===

{gcp-short} control plane and infrastructure node size for clusters created on or after 21 June 2024:
[options="header",cols="2a,2a,2a"]
|===
|Number of compute nodes
|Control plane size
|Infrastructure node size

|1 to 25
|n2-standard-8
|n2-highmem-4

|26 to 100
|n2-standard-16
|n2-highmem-8

|101 to 249
|n2-standard-32
|n2-highmem-16
|===

endif::[]

[NOTE]
====
The maximum number of compute nodes on
ifdef::openshift-rosa[]
{product-title}
endif::[]
ifdef::openshift-dedicated[]
{product-title}
endif::[]
clusters version 4.14.14 and later is 249. For earlier versions, the limit is 180.
====

[id="node-scaling-after-installation_{context}"]
== Node scaling after installation

If you change the number of compute nodes after installation, the control plane and infrastructure nodes are scaled by the Red{nbsp}Hat Site Reliability Engineering (SRE) team as required. The nodes are scaled to maintain platform stability.

Postinstallation scaling requirements for control plane and infrastructure nodes are assessed on a case-by-case basis. Node resource consumption and received alerts are taken into consideration.

.Rules for control plane node resizing alerts

The resizing alert is triggered for the control plane nodes in a cluster when the following occurs:

* Control plane nodes sustain over 66% utilization on average in a cluster.
+
[NOTE]
====
The maximum number of compute nodes on
ifdef::openshift-rosa[]
{product-title}
endif::[]
ifdef::openshift-dedicated[]
{product-title}
endif::[]
is 180.
====

.Rules for infrastructure node resizing alerts

Resizing alerts are triggered for the infrastructure nodes in a cluster when it has high-sustained CPU or memory utilization. This high-sustained utilization status is:

* Infrastructure nodes sustain over 50% utilization on average in a cluster with a single availability zone using 2 infrastructure nodes.
* Infrastructure nodes sustain over 66% utilization on average in a cluster with multiple availability zones using 3 infrastructure nodes.
+
[NOTE]
====
The maximum number of compute nodes on
ifdef::openshift-rosa[]
{rosa-title}
endif::[]
ifdef::openshift-dedicated[]
{product-title}
endif::[]
cluster versions 4.14.14 and later is 249. For earlier versions, the limit is 180.

The resizing alerts only appear after sustained periods of high utilization. Short usage spikes, such as a node temporarily going down causing the other node to scale up, do not trigger these alerts.
====

The SRE team might scale the control plane and infrastructure nodes for additional reasons, for example to manage an increase in resource consumption on the nodes.

ifdef::openshift-rosa[]
When scaling is applied, the customer is notified through a service log entry. For more information about the service log, see _Accessing the service logs for ROSA clusters_.
endif::[]

[id="sizing-considerations-for-larger-clusters_{context}"]
== Sizing considerations for larger clusters

For larger clusters, infrastructure node sizing can become a significant impacting factor to scalability. There are many factors that influence the stated thresholds, including the etcd version or storage data format.

Exceeding these limits does not necessarily mean that the cluster will fail. In most cases, exceeding these numbers results in lower overall performance.
