I believe there is a bug in the Get-NaDiskOwnership cmdlet. The documentation says:
Possible values are:
'all' which will list all disks.
'unowned' which will list all disks without owners.
'owned' which will list all disks with owners.
'unknown' which will list all disks with unknown owners.
'visible' which will list all disks belonging to the local and partner filer.
However, a Get-NaDiskOwner -OwnershipType 'unknown' returns an error: "Get-NaDiskOwner : Invalid ownership-type unknown"
All other ownership types work fine.
This is on PoSh Toolkit version 3.0. Could somebody please confirm if this is a bug?