Epic Goal*

LSO supports mpath disks with LocalVolumeSet, however if using discovery while there are mpath devices configured LSO does not provide good output (DiscoveryResult) which would clearly show which disks are backing mpath device.

Related issue that tracked adding mpath to DiscoveryResult: https://issues.redhat.com/browse/OCPBUGS-10884

Example: Having two disks (/dev/sda, /dev/sdb) configured to form mpath defined by ID: /dev/disk/by-id/dm-name-mpatha users will get a DiscoveryResult from which they can not see that /dev/sda, /dev/sdb are the ones backing dm-name-mpatha device - all entries look like distinct disks:

  discoveredDevices:
  - deviceID: /dev/disk/by-id/scsi-1Linux_scsi_debug_2001
    fstype: ""
    model: scsi_debug
    path: /dev/sda
    property: NonRotational
    serial: "2001"
    size: 10485760000
    status:
      state: NotAvailable
    type: disk
    vendor: Linux
  - deviceID: /dev/disk/by-id/dm-name-mpatha
    fstype: ""
    model: ""
    path: /dev/dm-0
    property: NonRotational
    serial: ""
    size: 10485760000
    status:
      state: Available
    type: mpath
    vendor: ""
  - deviceID: ""
    fstype: ""
    model: scsi_debug
    path: /dev/sdb
    property: NonRotational
    serial: "2001"
    size: 10485760000
    status:
      state: NotAvailable
    type: disk
    vendor: Linux

Why is this important? (mandatory)

This change would help improve user experience and simplify LSO discovery usage. Also we would reduce the chance that users try to use both mpath device and it's underlying disk for distinct volumes which might lead to data corruption.

The DiscoveryResult output is used by ODF UI to show users what disks are available, current output shows all disks but users can't tell which mpath devices are backed by which disks.

 
Scenarios (mandatory) 

As a cluster admin I want to increase network redundancy for disks that are managed by LSO LocalVolumeSet by using multipath. When disks are configured manually on the nodes I want LSO to produce a meaningful DiscoveryResult which will discover the mpath disks correctly and show it's backing disks without the need to investigate all the nodes and disks.

 
Dependencies (internal and external) (mandatory)

Internal: After this change is implemented OpenShift console needs to be patched to allow using all disk types at once (disk, partition, mpath).

External: None.

Contributing Teams(and contacts) (mandatory) 

Our expectation is that teams would modify the list below to fit the epic. Some epics may not need all the default groups but what is included here should accurately reflect who will be involved in delivering the epic.

• Development - yes
• Documentation - yes
• QE - yes
• PX - optional
• Others - optional

Acceptance Criteria (optional)

1. Unit tests
2. e2e tests
3. QE verification

Drawbacks or Risk (optional)

Drawback is that LSO would need refactoring to improve DiscoveryResult. Also the audience might be relatively small as the change would be mainly useful for ODF.

Done - Checklist (mandatory)

The following points apply to all epics and are what the OpenShift team believes are the minimum set of criteria that epics should meet for us to consider them potentially shippable. We request that epic owners modify this list to reflect the work to be completed in order to produce something that is potentially shippable.

• CI Testing -  Basic e2e automationTests are merged and completing successfully
• Documentation - Content development is complete.
• QE - Test scenarios are written and executed successfully.
• Technical Enablement - Slides are complete (if requested by PLM)
• Engineering Stories Merged
• All associated work items with the Epic are closed
• Epic status should be “Release Pending”