Scenario
UCS allows you to set resource limits for added containers during workload creation. You can apply for and limit the CPU and memory quotas used by each pod in the workload.
Configuration Description
- CPU quotas:
Table 1 Description of CPU quotas Parameter
Description
CPU request
Minimum number of CPU cores required by a container. Resources are scheduled for the container based on this value. The container can be scheduled to this node only when the total available CPU on the node is greater than or equal to the number of containerized CPU applications.
CPU limit
Maximum number of CPU cores available for a container.
Recommended configuration
Actual available CPU of a node ≥ Sum of CPU limits of all containers of the current pod ≥ Sum of CPU requests of all containers on the current pod. You can view the actual available CPUs of a node by choosing Clusters in the navigation pane, clicking the name of the target cluster, and choosing Nodes on the displayed page.
- Memory quotas:
Table 2 Description of memory quotas Parameter
Description
Memory request
Minimum amount of memory required by a container. Resources are scheduled for the container based on this value. The container can be scheduled to this node only when the total available memory on the node is greater than or equal to the number of containerized memory applications.
Memory Limit
Maximum amount of memory available for a container. When the memory usage exceeds the specified memory limit, the pod may be restarted, which affects the normal use of the workload.
Recommended configuration
Actual available memory of a node ≥ Sum of memory limits of all containers on the current pod ≥ Sum of memory requests of all containers on the current pod. You can view the actual available memory of a node by choosing Clusters in the navigation pane, clicking the name of the target cluster, and choosing Nodes on the displayed page.
The allocatable resources are calculated based on the resource request value (Request), which indicates the upper limit of resources that can be requested by pods on this node, but does not indicate the actual available resources of the node. The calculation formula is as follows:
- Allocatable CPU = Total CPU – Requested CPU of all pods – Reserved CPU for other resources
- Allocatable memory = Total memory – Requested memory of all pods – Reserved memory for other resources
Example
Assume that a cluster contains a node with 4 cores and 8 GB. A workload containing two pods has been deployed on the cluster. The resources of the two pods (pods 1 and 2) are as follows: {CPU request, CPU limit, memory request, memory limit} = {1 core, 2 cores, 2 GB, 2 GB}.
The CPU and memory usage of the node is as follows:
- Allocatable CPU = 4 cores - (1 core requested by pod 1 + 1 core requested by pod 2) = 2 cores
- Allocatable memory = 8 GB - (2 GB requested by pod 1 + 2 GB requested by pod 2) = 4 GB
The remaining 2 cores and 4 GB can be used by the next new pod.