Drawbacks of setting up HA over WAN (4269893)

There are some drawbacks of setting up HA over WAN 

The requirements section of the HA field guide explains how to configure HA to function outside of a subnet. However it should include the possible performance and reliability implication of setting up HA across multiple data centers.
There are a few concerns/challenges when the cluster is distributed across datacenters.

1. WAN links tend to have lower bandwidth than LANs. The low bandwidth and congestion across the WAN link may lead to false failovers.
2. If the database is not also distributed across datacenters, one of the nodes will be accessing the shared database remotely, which may have undesirable performance implications.
3. If the database is not also distributed across datacenters, an outage in the data center hosting the shared database will result in total failure of the cluster.

For more information please review the, High Availability Field Guide.

The above could potentially cause the cluster to form improperly and/or have issues in one FMS of the pair having difficulty coming up (extreme slowness).