5.3.2. Referring to devices with persistent names


  1. In some nodes, disk paths, such as /dev/sdb and /dev/sdc, might not point to the same block device during reboots. If this is the case with your Ceph Storage nodes, specify each disk with the /dev/disk/by-path/ symlink to ensure consistent block device mapping throughout your deployments:

          - /dev/disk/by-path/pci-0000:03:00.0-scsi-0:0:10:0
          - /dev/disk/by-path/pci-0000:03:00.0-scsi-0:0:11:0
          - /dev/nvme0n1
          - /dev/nvme0n1
  2. Optional: Because you must set the list of OSD devices before overcloud deployment, it might not be possible to identify and set the PCI path of disk devices. In this case, gather the /dev/disk/by-path/symlink data for block devices during introspection.

    In the following example, run the first command to download the introspection data from the undercloud Object Storage service (swift) for the server b08-h03-r620-hci and save the data in a file called b08-h03-r620-hci.json. Run the second command to grep for “by-path”. The output of this command contains the unique /dev/disk/by-path values that you can use to identify disks.

    (undercloud) [stack@b08-h02-r620 ironic]$ openstack baremetal introspection data save b08-h03-r620-hci | jq . > b08-h03-r620-hci.json
    (undercloud) [stack@b08-h02-r620 ironic]$ grep by-path b08-h03-r620-hci.json
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:0:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:1:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:3:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:4:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:5:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:6:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:7:0",
            "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:0:0",

For more information about naming conventions for storage devices, see Overview of persistent naming attributes in the Managing storage devices guide.