I was attempting to migrate from nfs to iscsi storage domains.  I have reached a state where I can no longer activate the old master storage domain, and thus no others will activate either. 

I'm ready to give up on the installation and just move to an HCI deployment instead.  Wipe all the hosts clean and start again. 

My plan was to create and use an export domain, then wipe the nodes and set them up HCI where I could re-import.  But without being able to activate a master domain, I can't create the export domain.

I'm not sure why it can't find the master anymore, as nothing has happened to the NFS storage, but the error in vdsm says it just can't find it:

StoragePoolMasterNotFound: Cannot find master domain: u'spUUID=5a77bed1-0238-030c-0122-0000000003b3, msdUUID=d3165759-07c2-46ae-b7b8-b6226a929d68'
2018-10-03 22:40:33,751-0700 INFO  (jsonrpc/3) [storage.TaskManager.Task] (Task='83f33db5-90f3-4064-87df-0512ab9b6378') aborting: Task is aborted: "Cannot find master domain: u'spUUID=5a77bed1-0238-030c-0122-0000000003b3, msdUUID=d3165759-07c2-46ae-b7b8-b6226a929d68'" - code 304 (task:1181)
2018-10-03 22:40:33,751-0700 ERROR (jsonrpc/3) [storage.Dispatcher] FINISH connectStoragePool error=Cannot find master domain: u'spUUID=5a77bed1-0238-030c-0122-0000000003b3, msdUUID=d3165759-07c2-46ae-b7b8-b6226a929d68' (dispatcher:82)
2018-10-03 22:40:33,751-0700 INFO  (jsonrpc/3) [jsonrpc.JsonRpcServer] RPC call StoragePool.connect failed (error 304) in 0.17 seconds (__init__:573)
2018-10-03 22:40:34,200-0700 INFO  (jsonrpc/1) [api.host] START getStats() from=::ffff:172.16.100.13,39028 (api:46)

When I look in cockpit on the hosts, the storage domain is mounted and seems fine.