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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 `Allocatable` on a Kubernetes node is defined as the amount of compute resources
that are available for pods. The scheduler does not over-subscribe that are available for pods. The scheduler does not over-subscribe
`Allocatable`. `CPU` and `memory` are supported as of now. Support for `storage` `Allocatable`. `CPU`, `memory` and `storage` are supported as of now.
is expected to be added in the future.
Node Allocatable is exposed as part of `v1.Node` object in the API and as part Node Allocatable is exposed as part of `v1.Node` object in the API and as part
of `kubectl describe node` in the CLI. of `kubectl describe node` in the CLI.
@ -81,7 +80,7 @@ be configured to use the `systemd` cgroup driver.
### Kube Reserved ### 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=` - **Kubelet Flag**: `--kube-reserved-cgroup=`
`kube-reserved` is meant to capture resource reservation for kubernetes system `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 ### 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=` - **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: Here is an example to illustrate Node Allocatable computation:
* Node has `32Gi` of `memory` and `16 CPUs` * Node has `32Gi` of `memory`, `16 CPUs` and `100Gi` of `Storage`
* `--kube-reserved` is set to `cpu=1,memory=2Gi` * `--kube-reserved` is set to `cpu=1,memory=2Gi,storage=1Gi`
* `--system-reserved` is set to `cpu=500m,memory=1Gi` * `--system-reserved` is set to `cpu=500m,memory=1Gi,storage=1Gi`
* `--eviction-hard` is set to `memory.available<500Mi` * `--eviction-hard` is set to `memory.available<500Mi,nodefs.available<10%`
Under this scenario, `Allocatable` will be `14.5 CPUs` & `28.5Gi` of memory. Under this scenario, `Allocatable` will be `14.5 CPUs`, `28.5Gi` of memory and
Scheduler ensures that the total `requests` across all pods on this node does `98Gi` of local storage.
not exceed `28.5Gi`. Kubelet evicts pods whenever the overall memory usage Scheduler ensures that the total memory `requests` across all pods on this node does
exceeds across pods exceed `28.5Gi`. If all processes on the node consume as 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`. 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 If `kube-reserved` and/or `system-reserved` is not enforced and system daemons
exceed their reservation, `kubelet` evicts pods whenever the overall node memory 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 ## 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 versions in order to ensure pods and their associated containers are launched in
the proper part of the cgroup hierarchy. 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`.