GlusterFS: Improve documentation

Signed-off-by: Jose A. Rivera <jarrpa@redhat.com>

1 files changed, 53 insertions, 8 deletions

diff --git a/roles/openshift_storage_glusterfs/README.md b/roles/openshift_storage_glusterfs/README.md
index 7b310dbf8..2e2b2497b 100644
--- a/roles/openshift_storage_glusterfs/README.md
+++ b/roles/openshift_storage_glusterfs/README.md
@@ -1,7 +1,26 @@
 OpenShift GlusterFS Cluster
 ===========================
 
-OpenShift GlusterFS Cluster Installation
+OpenShift GlusterFS Cluster Configuration
+
+This role handles the configuration of GlusterFS clusters. It can handle
+two primary configuration scenarios:
+
+* Configuring a new, natively-hosted GlusterFS cluster. In this scenario,
+  GlusterFS pods are deployed on nodes in the OpenShift cluster which are
+  configured to provide storage.
+* Configuring a new, external GlusterFS cluster. In this scenario, the
+  cluster nodes have the GlusterFS software pre-installed but have not
+  been configured yet. The installer will take care of configuring the
+  cluster(s) for use by OpenShift applications.
+* Using existing GlusterFS clusters. In this scenario, one or more
+  GlusterFS clusters are assumed to be already setup. These clusters can
+  be either natively-hosted or external, but must be managed by a
+  [heketi service](https://github.com/heketi/heketi).
+
+As part of the configuration, a particular GlusterFS cluster may be
+specified to provide backend storage for a natively-hosted Docker
+registry.
 
 Requirements
 ------------
@@ -21,13 +40,35 @@ hosted Docker registry:
 
 * `[glusterfs_registry]`
 
+Host Variables
+--------------
+
+For configuring new clusters, the following role variables are available.
+
+Each host in either of the above groups must have the following variable
+defined:
+
+| Name              | Default value | Description                             |
+|-------------------|---------------|-----------------------------------------|
+| glusterfs_devices | None          | A list of block devices that will be completely managed as part of a GlusterFS cluster. There must be at least one device listed. Each device must be bare, e.g. no partitions or LVM PVs. **Example:** '[ "/dev/sdb" ]'
+
+In addition, each host may specify the following variables to further control
+their configuration as GlusterFS nodes:
+
+| Name               | Default value             | Description                             |
+|--------------------|---------------------------|-----------------------------------------|
+| glusterfs_cluster  | 1                         | The ID of the cluster this node should belong to. This is useful when a single heketi service is expected to manage multiple distinct clusters. **NOTE:** For natively-hosted clusters, all pods will be in the same OpenShift namespace
+| glusterfs_hostname | openshift.common.hostname | A hostname (or IP address) that will be used for internal GlusterFS communication
+| glusterfs_ip       | openshift.common.ip       | An IP address that will be used by pods to communicate with the GlusterFS node
+| glusterfs_zone     | 1                         | A zone number for the node. Zones are used within the cluster for determining how to distribute the bricks of GlusterFS volumes. heketi will try to spread each volumes' bricks as evenly as possible across all zones
+
 Role Variables
 --------------
 
 This role has the following variables that control the integration of a
 GlusterFS cluster into a new or existing OpenShift cluster:
 
-| Name                                             | Default value           |                                         |
+| Name                                             | Default value           | Description                             |
 |--------------------------------------------------|-------------------------|-----------------------------------------|
 | openshift_storage_glusterfs_timeout              | 300                     | Seconds to wait for pods to become ready
 | openshift_storage_glusterfs_namespace            | 'default'               | Namespace in which to create GlusterFS resources
@@ -52,17 +93,21 @@ registry. These variables start with the prefix
 values in their corresponding non-registry variables. The following variables
 are an exception:
 
-| Name                                              | Default value         |                                         |
+| Name                                              | Default value         | Description                             |
 |---------------------------------------------------|-----------------------|-----------------------------------------|
 | openshift_storage_glusterfs_registry_namespace    | registry namespace    | Default is to use the hosted registry's namespace, otherwise 'default'
 | openshift_storage_glusterfs_registry_nodeselector | 'storagenode=registry'| This allows for the logical separation of the registry GlusterFS cluster from any regular-use GlusterFS clusters
 
 Additionally, this role's behavior responds to the following registry-specific
-variable:
-
-| Name                                         | Default value | Description                                                                  |
-|----------------------------------------------|---------------|------------------------------------------------------------------------------|
-| openshift_hosted_registry_glusterfs_swap     | False         | Whether to swap an existing registry's storage volume for a GlusterFS volume |
+variables:
+
+| Name                                          | Default value                | Description                             |
+|-----------------------------------------------|------------------------------|-----------------------------------------|
+| openshift_hosted_registry_glusterfs_endpoints | glusterfs-registry-endpoints | The name for the Endpoints resource that will point the registry to the GlusterFS nodes
+| openshift_hosted_registry_glusterfs_path      | glusterfs-registry-volume    | The name for the GlusterFS volume that will provide registry storage
+| openshift_hosted_registry_glusterfs_readonly  | False                        | Whether the GlusterFS volume should be read-only
+| openshift_hosted_registry_glusterfs_swap      | False                        | Whether to swap an existing registry's storage volume for a GlusterFS volume
+| openshift_hosted_registry_glusterfs_swapcopy  | True                         | If swapping, copy the contents of the pre-existing registry storage to the new GlusterFS volume
 
 Dependencies
 ------------