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47 lines
1.4 KiB
Plaintext
47 lines
1.4 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * etcd/etcd-performance.adoc
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:_mod-docs-content-type: CONCEPT
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[id="etcd-node-scaling_{context}"]
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= Node scaling for etcd
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In general, clusters must have 3 control plane nodes. However, if your cluster is installed on a bare metal platform, it can have up to 5 control plane nodes. If an existing bare-metal cluster has fewer than 5 control plane nodes, you can scale the cluster up as a postinstallation task.
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For example, to scale from 3 to 4 control plane nodes after installation, you can add a host and install it as a control plane node. Then, the etcd Operator scales accordingly to account for the additional control plane node.
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Scaling a cluster to 4 or 5 control plane nodes is available only on bare metal platforms.
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For more information about how to scale control plane nodes by using the Assisted Installer, see "Adding hosts with the API" and "Replacing a control plane node in a healthy cluster".
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[NOTE]
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====
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While adding control plane nodes can increase reliability and availability, it can decrease throughput and increase latency, affecting performance.
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====
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The following table shows failure tolerance for clusters of different sizes:
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.Failure tolerances by cluster size
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[%autowidth]
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|===
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|Cluster size |Majority |Failure tolerance
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|1 node
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|1
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|0
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|3 nodes
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|2
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|1
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|4 nodes
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|3
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|1
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|5 nodes
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|3
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|2
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|===
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For more information about recovering from quorum loss, see "Restoring to a previous cluster state".
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