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f24178b22d
This commit adds a recommendation around using volumes with high throughput to make sure kubelet and crio doesn't get overloaded when running heavy pods on the nodes.
60 lines
2.0 KiB
Plaintext
60 lines
2.0 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * scalability_and_performance/recommended-host-practices.adoc
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// * post_installation_configuration/node-tasks.adoc
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[id="recommended-node-host-practices_{context}"]
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= Recommended node host practices
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The {product-title} node configuration file contains important options. For
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example, two parameters control the maximum number of pods that can be scheduled
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to a node: `podsPerCore` and `maxPods`.
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When both options are in use, the lower of the two values limits the number of
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pods on a node. Exceeding these values can result in:
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* Increased CPU utilization.
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* Slow pod scheduling.
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* Potential out-of-memory scenarios, depending on the amount of memory in the node.
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* Exhausting the pool of IP addresses.
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* Resource overcommitting, leading to poor user application performance.
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[IMPORTANT]
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====
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In Kubernetes, a pod that is holding a single container actually uses two
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containers. The second container is used to set up networking prior to the
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actual container starting. Therefore, a system running 10 pods will actually
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have 20 containers running.
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====
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[NOTE]
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====
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Disk IOPS throttling from the cloud provider might have an impact on CRI-O and kubelet.
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They might get overloaded when there are large number of I/O intensive pods running on
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the nodes. It is recommended that you monitor the disk I/O on the nodes and use volumes
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with sufficient throughput for the workload.
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====
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`podsPerCore` sets the number of pods the node can run based on the number of
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processor cores on the node. For example, if `podsPerCore` is set to `10` on a
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node with 4 processor cores, the maximum number of pods allowed on the node will
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be `40`.
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[source,yaml]
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----
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kubeletConfig:
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podsPerCore: 10
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----
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Setting `podsPerCore` to `0` disables this limit. The default is `0`.
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`podsPerCore` cannot exceed `maxPods`.
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`maxPods` sets the number of pods the node can run to a fixed value, regardless
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of the properties of the node.
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[source,yaml]
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----
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kubeletConfig:
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maxPods: 250
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----
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