2.5. Defining the root disk for multi-disk clusters

Director must identify the root disk during provisioning in the case of nodes with multiple disks. For example, most Ceph Storage nodes use multiple disks. By default, director writes the overcloud image to the root disk during the provisioning process

There are several properties that you can define to help director identify the root disk:

  • model (String): Device identifier.
  • vendor (String): Device vendor.
  • serial (String): Disk serial number.
  • hctl (String): Host:Channel:Target:Lun for SCSI.
  • size (Integer): Size of the device in GB.
  • wwn (String): Unique storage identifier.
  • wwn_with_extension (String): Unique storage identifier with the vendor extension appended.
  • wwn_vendor_extension (String): Unique vendor storage identifier.
  • rotational (Boolean): True for a rotational device (HDD), otherwise false (SSD).
  • name (String): The name of the device, for example: /dev/sdb1.

Use the name property only for devices with persistent names. Do not use name to set the root disk for any other devices because this value can change when the node boots.

Complete the following steps to specify the root device using its serial number.


  1. Check the disk information from the hardware introspection of each node. Run the following command to display the disk information of a node:

    (undercloud) $ openstack baremetal introspection data save 1a4e30da-b6dc-499d-ba87-0bd8a3819bc0 | jq ".inventory.disks"

    For example, the data for one node might show three disks:

        "size": 299439751168,
        "rotational": true,
        "vendor": "DELL",
        "name": "/dev/sda",
        "wwn_vendor_extension": "0x1ea4dcc412a9632b",
        "wwn_with_extension": "0x61866da04f3807001ea4dcc412a9632b",
        "model": "PERC H330 Mini",
        "wwn": "0x61866da04f380700",
        "serial": "61866da04f3807001ea4dcc412a9632b"
        "size": 299439751168,
        "rotational": true,
        "vendor": "DELL",
        "name": "/dev/sdb",
        "wwn_vendor_extension": "0x1ea4e13c12e36ad6",
        "wwn_with_extension": "0x61866da04f380d001ea4e13c12e36ad6",
        "model": "PERC H330 Mini",
        "wwn": "0x61866da04f380d00",
        "serial": "61866da04f380d001ea4e13c12e36ad6"
        "size": 299439751168,
        "rotational": true,
        "vendor": "DELL",
        "name": "/dev/sdc",
        "wwn_vendor_extension": "0x1ea4e31e121cfb45",
        "wwn_with_extension": "0x61866da04f37fc001ea4e31e121cfb45",
        "model": "PERC H330 Mini",
        "wwn": "0x61866da04f37fc00",
        "serial": "61866da04f37fc001ea4e31e121cfb45"
  2. Enter openstack baremetal node set --property root_device= to set the root disk for a node. Include the most appropriate hardware attribute value to define the root disk.

    (undercloud) $ openstack baremetal node set --property root_device='{"serial":"<serial_number>"}' <node-uuid>

    For example, to set the root device to disk 2, which has the serial number 61866da04f380d001ea4e13c12e36ad6, enter the following command:

    (undercloud) $ openstack baremetal node set --property root_device='{"serial": "61866da04f380d001ea4e13c12e36ad6"}' 1a4e30da-b6dc-499d-ba87-0bd8a3819bc0

Ensure that you configure the BIOS of each node to include booting from the root disk that you choose. Configure the boot order to boot from the network first, then to boot from the root disk.

Director identifies the specific disk to use as the root disk. When you run the openstack overcloud deploy command, director provisions and writes the overcloud image to the root disk.