Support for FC Multipath disk configurations on OpenStack nodes

Many of real OpenStack production systems use external devices - which provide storage solutions. Most of them provide possibility to connect block devices using FC (Fiber Channel) HBA (Host Based Adapter) with multipath support.

FC HBA is an useful technology that can enable OpenStack to run more virtual machines (due high inputoutput productivity) and applications per server, reduce management time and server power draw and protect data from silent data corruption (usually, external data storage solution take care about data integrity and safety). FC HBA with multipath architect also increase high availability and stability of whole system.

Problem description

  • Fuel currently does not support any multipath solution, which creates all sorts of UX issues and blockers for deployment on such nodes.
  • Currently there is no possibility to deploy OpenStack on nodes with FC HBA multipath devices, using Fuel. Otherwise, many and many Openstack solutions are switching to use FC HBA solutions with multipath.
  • Currently there is no possibility to deploy OpenStack by Fuel on nodes, which have only FC HBA storage.

Proposed changes

The field analysis showed that FC HBA multipath is more frequent use case than iSCSI, so this proposal is to implement support for FC HBA multipath disks in Fuel 9.0, which means at least the following:

  • enable of FC HBA multipath devices support in bootstraptarget system. Multipath support should be enabled in Fuel by default
  • change fuel-nailgun-agent to send discovered multipath topology in Nailgun
  • export of multipath device info into UI as a single block device
  • extend fuel-agent to enable provisioning nodes with multipath devices. It requires to fix issue with naming of partitions on multipath devices.

Web UI

Recognized multipath configuration will be available on Web UI, for each node, in the node information dialog. Each multipath device will be exported as a single block device.


Disk configuration reported by fuel-nailgun-agent will be stored, as it works now, as a part of Node DB instance metadata. Disk configuration will be displayed in Web UI as is.


We propose to extend fuel-nailgun-agent with support for multipath devices. That means, that fuel-nailgun-agent will be able to handle not only physical block devices, but also /dev/mapper/* and /dev/mpath/* devices - which will be populated by multipath service.

For example, a node with two HBAs attached to a storage controller with two ports via a single unzoned FC HBA switch sees four devices: /dev/sda, /dev/sdb, /dev/sdc, and /dev/sdd. DM-Multipath creates a single device with a unique WWID (WWN) that reroutes I/O to those four underlying devices according to the multipath configuration.

We suggest adding logic in fuel-nailgun-agent to discover and report multipath topology in following format:

 [{'name': 'dm-42',
   'model': '',
   'removable': '0',
   'size': 53687091200,
   'extra': ['disk/by-id/dm-uuid-mpath-42']
   'multipaths':['sda', 'sdb']},...

Underlying devices (in current sample - sda and sdb) will not be reported into nailgun as a separate block device. Metadata for not multipatch devices will not be changed.


We propose to extend default fuel-bootstrap build with new packages and parameters needed for multipath support.

Support for HBA card will be provided by Ubuntu distribution or driver delivered by user to bootstrap during build process. User can manually rebuild bootstrap with required driver package.


We propose to extend fuel-agent to enable provisioning nodes with multipath devices. It requires to fix issue with naming of partitions on multipath devices.

Data model






RPC Protocol


Fuel Client




Fuel Library



Alternative solution is following fuel-nailgun-agent should be extended to provide parsed output from commands

`dmsetup info -c --nameprefixes --noheadings --rows -o name,uuid,blkdevname,blkdevs_used`
`udevadm info --query=property --export --name=#{device_name}`

as for discovered block devices. It should be enough to determingite the multipath configuration on server side.

New version of fuel-nailgun-agent report will look this:

          "removable": "0",
          "size": 53687091200,
            "DEVLINKS":"/dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_35e53b2cb5114d80b28b /dev/disk/by-path/pci-0000:00:09.0-scsi-0:0:0:0",
            "ID_BUS": "scis",
            "ID_MODEL": "Toshiba",
      "dmsetup_info": {
        "DM_NAME":"0QEMU    QEMU HARDDISK   35e53b2cb5114d80b28b",
        "DM_UUID":"mpath-0QEMU    QEMU HARDDISK   35e53b2cb5114d80b28b",

Reports in new format will be handled by url “/api/v1/nodes/agent/”. To handle new report format API microversion v1.1 will be pointed in HTTP handlers, like OpenStack components do. New API handler should be available to receive and process data about nodes disks from the fuel-nailgun-agent.

Only disk part of report will be changed. Received data will be processed and stored as part of Node DB instance metadata in the format compatible with current Nailgun UI. Output of REST API will not be changed.

Upgrade impact


Security impact


Notifications impact


End user impact


Performance impact

We are not expecting any problems related with default installation (wo FC HBA multipath system). All others impact can be related only with FC HBA multipath system itself.

Deployment impact

We propose to add possibility to attach disk via multipath and FC HBA for nodes. Disks will be available on fuel ui, and normally processed like physical disks. This feature don’t have any impact on previous installations, only extend disks support.

Developer impact


Infrastructure impact


Documentation impact

User will be informed that:
  • functionality is available in Fuel
  • how to generate bootstrap with user HBA card driver (custom driver, not delivered with Ubuntu-kernel)



Primary assignee:
Szymon Banka
Other contributors:
Krzysztof Szukielojc Sergey Slipushenko Aleksey Zvyagintsev
QA engineers
Alexander Zatserklyany
Mandatory design review:
Alexander Gordeev Vladimir Kozhukalov

Work Items

  • extend fuel-ui to show multipath disks
  • add packages related to multipath support into default ubuntu-bootstrap image
  • add fuel-nailgun-agent support for correct multipath disk discovery
  • add to nailgun support for correct serialization of disks delivered by multipath



Testing, QA

Proper functional tests should be implemented.

Acceptance criteria

  • Multipath devices automatically detected and configured during node bootstrap
  • Host OS able to boot from FC HBA multipath disk devices
  • OpenStack deployed on nodes with multipath devices
  • Auto-tests implemented