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5.4. Defining the Root Disk for Nodes

Some nodes might use multiple disks. This means the director needs to identify the disk to use for the root disk during provisioning. There are several properties you can use to help the director identify the root disk:
  • model (String): Device identifier.
  • vendor (String): Device vendor.
  • serial (String): Disk serial number.
  • wwn (String): Unique storage identifier.
  • hctl (String): Host:Channel:Target:Lun for SCSI.
  • size (Integer): Size of the device in GB.
In this example, you specify the drive to deploy the Overcloud image using the serial number of the disk to determine the root device.
First, collect a copy of each node's hardware information that the director obtained from the introspection. This information is stored in the OpenStack Object Storage server (swift). Download this information to a new directory:
$ mkdir swift-data
$ cd swift-data
$ export IRONIC_DISCOVERD_PASSWORD=`sudo grep admin_password /etc/ironic-inspector/inspector.conf | awk '! /^#/ {print $NF}'`
$ for node in $(ironic node-list | awk '!/UUID/ {print $2}'); do swift -U service:ironic -K $IRONIC_DISCOVERD_PASSWORD download ironic-inspector inspector_data-$node; done
This downloads the data from each inspector_data object from introspection. All objects use the node UUID as part of the object name:
$ ls -1
Check the disk information for each node. The following command displays each node ID and the disk information:
$ for node in $(ironic node-list | awk '!/UUID/ {print $2}'); do echo "NODE: $node" ; cat inspector_data-$node | jq '.inventory.disks' ; echo "-----" ; done
For example, the data for one node might show three disk:
NODE: 46b90a4d-769b-4b26-bb93-50eaefcdb3f4
    "size": 1000215724032,
    "vendor": "ATA",
    "name": "/dev/sda",
    "model": "WDC WD1002F9YZ",
    "wwn": "0x0000000000000001",
    "serial": "WD-000000000001"
    "size": 1000215724032,
    "vendor": "ATA",
    "name": "/dev/sdb",
    "model": "WDC WD1002F9YZ",
    "wwn": "0x0000000000000002",
    "serial": "WD-000000000002"
    "size": 1000215724032,
    "vendor": "ATA",
    "name": "/dev/sdc",
    "model": "WDC WD1002F9YZ",
    "wwn": "0x0000000000000003",
    "serial": "WD-000000000003"
For this example, set the root device to disk 2, which has WD-000000000002 as the serial number. This requires a change to the root_device parameter for the node definition:
$ ironic node-update 97e3f7b3-5629-473e-a187-2193ebe0b5c7 add properties/root_device='{"serial": "WD-000000000002"}'
This helps the director identify the specific disk to use as the root disk. When we initiate our Overcloud creation, the director provisions this node and writes the Overcloud image to this disk.


Make sure to configure the BIOS of each node to include booting from the chosen root disk. The recommended boot order is network boot, then root disk boot.


Do not use name to set the root disk as this value can change when the node boots.