How can I support a multiple data center deployment without Ethernet Layer 2 Adjacency between them?

Solution may be to implement a third party ADC, or upgrade the shared network.

One possible solution is to introduce a third party ADC to solve the problem of redundancy between the two data centers. See the Non-Layer 2 Adjacent type deployment section in this page.

Alternatively, the network between the two datacenters could be upgraded to support Ethernet Layer 2 Adjacency by one of several method options as described in How do I span Layer 2 Adjacency across the data centers?.