add storagecall docs

docs/_managedk8s/FAQ/storageclass/index.en.md

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+---
+title: StorageClass Setup
+lang: "en"
+permalink: /managedk8s/storageclasses/
+nav_order: 4200
+parent: FAQ
+---
+# StorageClass Setup
+
+We provide one default storage class per Cluster.
+> **Caution:**
+> This is managed by WIIT and can be **overwritten at any time**. Please create a separate storage class for your changes.
+
+```
+kubectl get storageclasses.storage.k8s.io
+NAME                   PROVISIONER                AGE
+cinder-csi (default)   cinder.csi.openstack.org   6h45m
+```
+
+## Openstack Volume Types
+
+The Openstack volume types sorted by maximum possible IOPS:
+
+* low-iops
+* default <- used in the default class
+* high-iops
+
+### Adding Your Own Classes
+
+If you need use one of the other types, you can add your own definitions.
+
+Example:
+
+```
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: my-high-iops-class
+provisioner: cinder.csi.openstack.org
+parameters:
+  type: high-iops
+```
+
+Apply with `kubectl apply -f storage-class.yaml`.
+
+* `name`: Choose a unique one, as we don't want to interfere with the default names.
+* `provisioner`: Use the one of your cluster. You can always have a look in the default class to verify the right provider.
+* `type`: Use one of the [official provided types](/optimist/specs/volume_specification/#volume-type-list) from the Optimist platform (at the time of writing low-iops and high-iops).
+
+To use the new storage class you need to change your volumes definitions and add the new StorageClass name.