1. You need to format this disk on first host only.
2. On second host, once you configure ISCSI adapter and static or dynamic discovery correctly, you just need to re-scan storage adapter to discover newly presented datastore because you already have formatted this target as VMFS while configuring on first host.
Make sure on second host your'e not following 'Creating new Datastore' Wizard. Just re scan storage adapters on second host. Select Host > Configure > Storage Devices > Rescan all storage adapters. Then datastore should mount itself on second host.
