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Merge pull request #4145 from vishh/document-storage-allocatable 

Adding storage as a supported resource to node allocatable
reviewable/pr4151/r1
Andrew Chen 2017-06-20 16:18:53 -07:00 committed by GitHub
parent 91ecf67ad4 33a3638d5b
commit e0ad6ebf6b
1 changed files with 16 additions and 13 deletions
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29
docs/tasks/administer-cluster/reserve-compute-resources.md
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@ -45,8 +45,7 @@ on each node.
`Allocatable` on a Kubernetes node is defined as the amount of compute resources
that are available for pods. The scheduler does not over-subscribe
`Allocatable`. `CPU` and `memory` are supported as of now. Support for `storage`
is expected to be added in the future.
`Allocatable`. `CPU`, `memory` and `storage` are supported as of now.
Node Allocatable is exposed as part of `v1.Node` object in the API and as part
of `kubectl describe node` in the CLI.
@ -81,7 +80,7 @@ be configured to use the `systemd` cgroup driver.
### Kube Reserved
- **Kubelet Flag**: `--kube-reserved=[cpu=100m][,][memory=100Mi]`
- **Kubelet Flag**: `--kube-reserved=[cpu=100m][,][memory=100Mi][,][storage=1Gi]`
- **Kubelet Flag**: `--kube-reserved-cgroup=`
`kube-reserved` is meant to capture resource reservation for kubernetes system
@ -111,7 +110,7 @@ exist. Kubelet will fail if an invalid cgroup is specified.
### System Reserved
- **Kubelet Flag**: `--system-reserved=[cpu=100mi][,][memory=100Mi]`
- **Kubelet Flag**: `--system-reserved=[cpu=100mi][,][memory=100Mi][,][storage=1Gi]`
- **Kubelet Flag**: `--system-reserved-cgroup=`
@ -194,20 +193,22 @@ So expect a drop in `Allocatable` capacity in future releases.
Here is an example to illustrate Node Allocatable computation:
* Node has `32Gi` of `memory` and `16 CPUs`
* `--kube-reserved` is set to `cpu=1,memory=2Gi`
* `--system-reserved` is set to `cpu=500m,memory=1Gi`
* `--eviction-hard` is set to `memory.available<500Mi`
* Node has `32Gi` of `memory`, `16 CPUs` and `100Gi` of `Storage`
* `--kube-reserved` is set to `cpu=1,memory=2Gi,storage=1Gi`
* `--system-reserved` is set to `cpu=500m,memory=1Gi,storage=1Gi`
* `--eviction-hard` is set to `memory.available<500Mi,nodefs.available<10%`
Under this scenario, `Allocatable` will be `14.5 CPUs` & `28.5Gi` of memory.
Scheduler ensures that the total `requests` across all pods on this node does
not exceed `28.5Gi`. Kubelet evicts pods whenever the overall memory usage
exceeds across pods exceed `28.5Gi`. If all processes on the node consume as
Under this scenario, `Allocatable` will be `14.5 CPUs`, `28.5Gi` of memory and
`98Gi` of local storage.
Scheduler ensures that the total memory `requests` across all pods on this node does
not exceed `28.5Gi` and storage doesn't exceed `88Gi`.
Kubelet evicts pods whenever the overall memory usage exceeds across pods exceed `28.5Gi`,
or if overall disk usage exceeds `88Gi` If all processes on the node consume as
much CPU as they can, pods together cannot consume more than `14.5 CPUs`.
If `kube-reserved` and/or `system-reserved` is not enforced and system daemons
exceed their reservation, `kubelet` evicts pods whenever the overall node memory
usage is higher than `31.5Gi`.
usage is higher than `31.5Gi` or `storage` is greater than `90Gi`
## Feature Availability
@ -231,3 +232,5 @@ required to drain their nodes prior to upgrade of the `kubelet` from prior
versions in order to ensure pods and their associated containers are launched in
the proper part of the cgroup hierarchy.
As of Kubernetes version 1.7, `kubelet` supports specifying `storage` as a resource
for `kube-reserved` and `system-reserved`.