[Docs] Deployment guide for Persistent Memory (PMEM)

Adding guide to document how to manage overcloud nodes
with PMEM and configure the overcloud to use vPMEM Nova feature [0].

[0]: https://docs.openstack.org/nova/latest/admin/virtual-persistent-memory.html

Change-Id: Iec37d2d246c4b4bbec0154d8cf12badd22dd8d7d

deploy-guide/source/features/compute_nvdimm.rst

@@ -0,0 +1,83 @@
+Manage Virtual Persistent Memory (vPMEM)
+=====================================================
+Virtual Persistent Memory (vPMEM) is a Nova feature that allows to expose
+Persistent Memory (PMEM) namespaces to guests using libvirt compute driver.
+This guide show how the vPMEM feature is supported in TripleO deployment
+framework. For in-depth description of Nova's vPMEM feature check Nova
+documentation: `Attaching virtual persistent memory to guests
+<https://docs.openstack.org/nova/latest/admin/virtual-persistent-memory.html>`_
+
+.. warning::
+
+  vPMEM feature is only available in Train(20.0.0) or later releases.
+
+.. contents::
+  :depth: 3
+  :backlinks: none
+
+Prerequisite
+------------
+Operators needs to properly configured PMEM Hardware before deploying Overcloud
+with vPMEM support. Example of such a hardware is Intel Optane DC Persistent Memory.
+Intel provides tool (`ipmctl <https://software.intel.com/en-us/articles/quick-start-guide-configure-intel-optane-dc-persistent-memory-on-linux>`_)
+to configure the PMEM hardware.
+
+Operators need to configure the hardware in such a way to enable TripleO to create
+`PMEM namespaces <http://pmem.io/ndctl/ndctl-create-namespace.html>`_ in **devdax** mode.
+TripleO currently support one backend NVDIMM region, so in case of multiple NVDIMMs
+Interleaved Region needs to be configured.
+
+TripleO vPMEM parameters
+------------------------
+
+Following parameter are used within TripleO to configure vPMEM:
+
+    .. code::
+
+        NovaPMEMMappings:
+          type: string
+          description: >
+            PMEM namespace mappings as backend for vPMEM feature. This parameter
+            sets Nova's `pmem_namespaces` configuration options. PMEM namespaces
+            needs to be create manually or with conjunction with `NovaPMEMNamespaces`
+            parameter.
+            Requires format: $LABEL:$NSNAME[|$NSNAME][,$LABEL:$NSNAME[|$NSNAME]].
+          default: ""
+          tags:
+            - role_specific
+        NovaPMEMNamespaces:
+          type: string
+          description: >
+            Creates PMEM namespaces on the host server using `ndctl` tool
+            through Ansible.
+            Requires format: $SIZE:$NSNAME[,$SIZE:$NSNAME...].
+            $SIZE supports the suffixes "k" or "K" for KiB, "m" or "M" for MiB, "g"
+            or "G" for GiB and "t" or "T" for TiB.
+            NOTE: This requires properly configured NVDIMM regions and enough space
+            for requested namespaces.
+          default: ""
+          tags:
+            - role_specific
+
+Both parameters are role specific and should be used with custom role. Please check documentation on
+how to use `Role-Specific Parameters <https://docs.openstack.org/project-deploy-guide/tripleo-docs/latest/features/role_specific_parameters.html>`_.
+
+Examples
+--------
+    .. code::
+
+        parameter_defaults:
+          ComputePMEMParameters:
+            NovaPMEMMappings: "6GB:ns0|ns1|ns2,LARGE:ns3"
+            NovaPMEMNamespaces: "6G:ns1,6G:ns1,6G:ns2,100G:ns3"
+
+
+The following example will peform following steps:
+* ensure **ndctl** tool is installed on hosts with role **ComputePMEM**
+* create PMEM namespaces as specified in the **NovaPMEMNamespaces** parameter.
+- ns0, ns1, ns2 with size 6GiB
+- ns3 with size 100GiB
+* set Nova prameter **pmem_namespaces** in nova.conf to map create namespaces to vPMEM as specified in **NovaPMEMMappings**.
+In this example the label '6GB' will map to one of ns0, ns1 or ns2 namespace and the label 'LARGE' will map to ns3 namespace.
+
+After deployment you need to configure flavors as described in documentation `Nova: Configure a flavor <https://docs.openstack.org/nova/latest/admin/virtual-persistent-memory.html#configure-a-flavor>`_

deploy-guide/source/features/index.rst

@@ -11,6 +11,7 @@ Documentation on additional features for |project|.
    composable_services
    custom_networks
    custom_roles
+   compute_nvdimm
    deploy_cellv2
    deploy_swift
    deployed_server