Aggregate in “Unknown” State After Motherboard Replacement

• ONTAP 9
• AFF and FAS systems

• After motherboard replacement on both controllers in HA pair, the data aggregate on one Node was reported in an “unknown” state. 
  Cluster::> aggr show
  

  Aggregate     Size  Available  Used% State     #Vols  Nodes       RAID Status

  --------- -------- --------- ----- ------- ------ ---------------- ------------
aggr1          -        -       -    unknown     -    Node1        -      -

The aggregate was visible in VLDB but missing in WAFL, and disk ownership metadata showed old system IDs still associated with some disks.

cluster::*>debug vreport show 

aggregate Differences:

Name             Reason   Attributes
--------         -------  ---------------------------------------------------
 aggr1         Present in VLDB Only

                          Node Name: Node1

                          Aggregate UUID: acdxxxx-3xx6-4xx4-8305-bdxxxx22809

                          Aggregate State: unknown

                          Aggregate Raid Status:

                          Aggregate HA Policy:

                          Is Aggregate Root: false

                          Is Composite Aggregate: false

volume Differences:
Name             Reason   Attributes

--------         -------  ---------------------------------------------------

cluster:SITE_ctrlSAN_COMVAULT_1 Present in VLDB and aggregate not online

                          Node Name: Node1

                          Volume DSID:1029 MSID:21xxx7xx10

                          UUID: unknown

                          Aggregate Name: aggr1

                          Aggregate UUID: acdxxxx-3xx6-4xx4-8305-bdxxxx22809

                          Vserver UUID: acdxxxx-3xx6-4xx4-8305-bdxxxx22809

                          AccessType: READ_WRITE

                          StorageType: REGULAR

                          Constituent Role: none

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