How should a federation be configured when a primary ECS VDC already exists?

First configure the secondary ECS as standalone and then add the VDC to the federation.

First create the storage pool on the secondary ECS and then configure it on the primary ECS of the federation.

First get the VDC access key from the primary ECS of the federation and then add it to the secondary VDC.

Add the secondary VDC to the federation during fabric and HAL installation.