It's not a local file, e.g.
a) XCP node is utility-mgmt-003
b) NFS servers are utility-mgmt-002 (PROD) and utility-mgmt-004 (DR site)
In this scenario Catalog would be on an NFS export at DR site.
I think the reason Catalog is on external (source, target, or some other) NFS share is that multiple XCP nodes can access it at the same time.
If you can't get this to work as I described, I'll try tomorrow using the latest XCP version.