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

Warning

vPMEM feature is only available in Train(20.0.0) or later releases.

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) to configure the PMEM hardware.

Operators need to configure the hardware in such a way to enable TripleO to create PMEM namespaces 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:

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.

Examples

parameter_defaults:
  ComputePMEMParameters:
    NovaPMEMMappings: "6GB:ns0|ns1|ns2,LARGE:ns3"
    NovaPMEMNamespaces: "6G:ns1,6G:ns1,6G:ns2,100G:ns3"

The following example will perform 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 parameter 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