Chapter 29. Configuring ephemeral storage
29.1. Overview
OpenShift Container Platform can be configured to allow management of ephemeral storage of pod and container working data. While containers have been able to utilize writable layers, logs directories, and EmptyDir volumes, this storage has been subject to a number of limitations, as discussed here.
Ephemeral storage management permits administrators to limit the resources consumed by individual pods and containers, and for pods and containers to specify requests and limits on their use of such ephemeral storage. This is a technology preview and is disabled by default.
This technology preview does not change any of the mechanisms for making local storage available in OpenShift Container Platform; the existing mechanisms, root directory or runtime directory, still apply. This technology preview only provides a mechanism for managing the use of this resource.
29.2. Enabling ephemeral storage
To enable ephemeral storage:
Edit or create the master configuration file on all masters, /etc/origin/master/master-config.yaml by default, and add
LocalStorageCapacityIsolation=true
in theapiServerArguments
andcontrollerArguments
sections:apiServerArguments: feature-gates: - LocalStorageCapacityIsolation=true ... controllerArguments: feature-gates: - LocalStorageCapacityIsolation=true ...
Edit the ConfigMap for all nodes to enable the LocalStorageCapacityIsolation on the command line. You can identify the ConfigMaps that need to be edited as follows:
$ oc get cm -n openshift-node NAME DATA AGE node-config-compute 1 52m node-config-infra 1 52m node-config-master 1 52m
For each of these maps,
node-config-compute
,node-config-infra
, andnode-config-master
, you need to add the feature gate:oc edit cm node-config-master -n openshift-node
If there is already a
feature-gates:
declaration, add the following text to the list of feature gates:,LocalStorageCapacityIsolation=true
If there is no
feature-gates:
declaration, add the following section:feature-gates: - LocalStorageCapacityIsolation=true
-
Repeat for
node-config-compute
,node-config-infra
, and any other ConfigMaps. - Restart OpenShift Container Platform and delete the container running the apiserver.
Omitting any of these steps may result in ephemeral storage management not being enabled.