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+# Installing a NFS-provisioner
+
+The Gerrit replica requires access to a persistent volume capable of running in
+`Read Write Many (RWM)`-mode to store the git repositories, since the repositories
+have to be accessed by mutiple pods. One possibility to provide such volumes
+is to install a provisioner for NFS-volumes into the same Kubernetes-cluster.
+This document will guide through the process.
+
+The [Kubernetes external-storage project](https://github.com/kubernetes-incubator/external-storage)
+provides an out-of-tree dynamic [provisioner](https://github.com/kubernetes-incubator/external-storage/tree/master/nfs)
+for NFS volumes. A chart exists for easy deployment of the project onto a
+Kubernetes cluster. The chart's sources can be found [here](https://github.com/helm/charts/tree/master/stable/nfs-server-provisioner).
+
+## Prerequisites
+
+This guide will use Helm to install the NFS-provisioner. Thus, Helm has to be
+installed.
+
+## Installing the nfs-server-provisioner chart
+
+A custom `values.yaml`-file containing a configuration tested with the
+gerrit-replica chart can be found in the `supplements/nfs`-directory in the
+gerrit-replica chart's root directory. In addition a file stating the tested
+version of the nfs-server-provisioner chart is present in the same directory.
+
+If needed, adapt the `values.yaml`-file for the nfs-server-provisioner chart
+further and then run:
+
+```sh
+cd $(git rev-parse --show-toplevel)/helm-charts/gerrit-replica/supplements/nfs
+helm install nfs \
+ stable/nfs-server-provisioner \
+ -f values.yaml \
+ --version $(cat VERSION)
+```
+
+For a description of the configuration options, refer to the
+[chart's documentation](https://github.com/helm/charts/blob/master/stable/nfs-server-provisioner/README.md).
+
+Here are some tips for configuring the nfs-server-provisioner chart to work with
+the gerrit-replica chart:
+
+- Deploying more than 1 `replica` led to some reliability issues in tests and
+ should be further tested for now, if required.
+- The name of the StorageClass created for NFS-volumes has to be the same as the
+ one defined in the gerrit-replica chart for `storageClasses.shared.name`
+- The StorageClas for NFS-volumes needs to have the parameter `mountOptions: vers=4.1`,
+ due to compatibility [issues](https://github.com/kubernetes-incubator/external-storage/issues/223)
+ with Ganesha.
+
+## Deleting the nfs-server-provisioner chart
+
+***note
+**Attention:** Never delete the nfs-server-provisioner chart, if there is still a
+PersistentVolumeClaim and Pods using a NFS-volume provisioned by the NFS server
+provisioner. This will lead to crashed pods, that will not be terminated correctly.
+***
+
+If no Pod or PVC is using a NFS-volume provisioned by the NFS server provisioner
+anymore, delete it like any other chart:
+
+```sh
+helm delete nfs
+```