Help Center/ Cloud Container Engine/ User Guide/ Nodes/ Node O&M/ Node Resource Reservation Rules
Updated on 2025-07-17 GMT+08:00
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Node Resource Reservation Rules

Some node resources are used to run mandatory Kubernetes system components and resources to make the node as part of your cluster. Therefore, the total number of node resources and the number of allocatable node resources for your cluster are different. The larger the node specifications, the more the containers deployed on the node. Therefore, more node resources need to be reserved to run Kubernetes components.

To maintain node stability, a specific number of CCE node resources will be reserved for Kubernetes components like kubelet, kube-proxy, and docker, based on the node specifications.

CCE calculates the resources that can be allocated to user nodes as follows:

Allocatable resources = Total amount - Reserved amount - Eviction threshold

The memory eviction threshold is fixed at 100 MiB.

Total amount indicates the available memory of the ECS, excluding the memory used by system components. Therefore, it is slightly less than the total memory of the node flavor. For details, see Why Is the Memory of an ECS Obtained by Running the free Command Inconsistent with the Actual Memory?

When the memory consumed by all pods on a node increases, the following behaviors may occur:

  1. When the available memory of the node is lower than the eviction threshold, kubelet is triggered to evict pods. For details about the eviction threshold in Kubernetes, see Node-pressure Eviction.
  2. If a node triggers an OS memory insufficiency event (OOM) before kubelet reclaims memory, the system terminates the container. Unlike pod eviction, kubelet restarts the container based on the pod's RestartPolicy.

Relationship Between Node Resource Reservation and Cluster Versions

Cluster Version

Specific Version

Node Memory Reservation

Node CPU Reservation

Node Data Disk Reservation

v1.29 or later

None

Node Memory Reservation Rule v2

Node CPU Reservation Rules

Node Data Disk Reservation Rules

v1.28

v1.28.2-r0 or later

Node Memory Reservation Rule v2

Earlier than v1.28.2-r0

v1.27

v1.27.4-r0 or later

Node Memory Reservation Rule v2

Earlier than v1.27.4-r0

v1.25

v1.25.7-r0 or later

Node Memory Reservation Rule v2

Earlier than v1.25.7-r0

v1.23

v1.23.12-r0 or later

Node Memory Reservation Rule v2

v1.23.3-r0 or later, or versions earlier than v1.23.12-r0

Earlier than v1.23.3-r0

Node Memory Reservation Rule v1

v1.21

v1.21.13-r0 or later

Node Memory Reservation Rule v2

v1.21.4-r0 or later, or versions earlier than v1.21.13-r0

Earlier than v1.21.4-r0

Node Memory Reservation Rule v1

Node Memory Reservation Rule v1

You can use the following formula calculate how much memory you should reserve for running containers on a node:

Total reserved amount = Reserved memory for system components + Reserved memory for kubelet to manage pods

Table 1 Reservation rules for system components

Total Memory (TM)

Reserved Memory for System Components

TM ≤ 8 GiB

0 MiB

8 GiB < TM ≤ 16 GiB

[(TM – 8 GiB) x 1024 x 10%] MiB

16 GiB < TM ≤ 128 GiB

[8 GiB x 1024 x 10% + (TM – 16 GiB) x 1024 x 6%] MiB

TM > 128 GiB

(8 GiB x 1024 x 10% + 112 GiB x 1024 x 6% + (TM – 128 GiB) x 1024 x 2%) MiB
Table 2 Reservation rules for kubelet

Total Memory (TM)

Number of Pods

Reserved Memory for kubelet

TM ≤ 2 GiB

None

TM x 25%

TM > 2 GiB

0 < Max. pods on a node ≤ 16

700 MiB

16 < Max. pods on a node ≤ 32

[700 + (Max. pods on a node – 16) x 18.75] MiB

32 < Max. pods on a node ≤ 64

[1024 + (Max. pods on a node – 32) x 6.25] MiB

64 < Max. pods on a node ≤ 128

[1230 + (Max. pods on a node – 64) x 7.80] MiB

Max. pods on a node > 128

[1740 + (Max. pods on a node – 128) x 11.20] MiB

For a small-capacity node, adjust the maximum number of instances based on the site requirements. Alternatively, when creating a node on the CCE console, you can adjust the maximum number of instances for the node based on the node specifications.

Node Memory Reservation Rule v2

The total reserved memory of a CCE node using memory reservation rule v2 includes memory allocated for system components and Kubernetes.

Reserved memory includes basic and floating parts. For the OS, the floating memory depends on the node specifications. For CCE, the floating memory depends on the number of pods on a node.

By default, CCE automatically calculates the reserved memory based on the rules listed in Table 3. You can customize the reserved memory by configuring parameters system-reserved-mem and kube-reserved-mem in the node pool settings. For details, see Modifying Node Pool Configurations.

Table 3 Node memory reservation rule v2

Memory Reserved for

Basic/Floating

Reservation

Used by

System components

Basic

Fixed at 400 MiB

OS service components such as sshd and systemd-journald.

Floating (depending on the node memory)

25 MiB/GiB

Kernel

Kubernetes

Basic

Fixed at 500 MiB

Container engine components, such as kubelet and kube-proxy, when the node is unloaded

Floating (depending on the number of pods on the node)

Docker: 20 MiB/Pod

containerd: 5 MiB/Pod

Container engine components when the number of pods increases

NOTE:

When the v2 model reserves memory for a node by default, the default maximum number of pods is estimated based on the memory. For details, see Table 1.

Node CPU Reservation Rules

Table 4 Node CPU reservation rules

Total CPU Cores (Total)

Reserved CPU Cores

Total ≤ 1 core

Total x 6%

1 core < Total ≤ 2 cores

1 core x 6% + (Total – 1 core) x 1%

2 cores < Total ≤ 4 cores

1 core x 6% + 1 core x 1% + (Total – 2 cores) x 0.5%

Total > 4 cores

1 core x 6% + 1 core x 1% + 2 cores x 0.5% + (Total – 4 cores) x 0.25%

Node Data Disk Reservation Rules

CCE uses Logical Volume Manager (LVM) for disk management. LVM creates a metadata area on a disk to store logical and physical volume information, occupying 4 MiB of space. Therefore, the actual available disk space of a node is the disk size minus 4 MiB.

Parent Topic: Node O&M