Building a geographically dispersed SQL Server cluster to host SharePoint relies on third-party applications to overcome the 'same subnet' limitation. A self-sufficient storage replication infrastructure that is outside the Microsoft product line also relies on third-party applications to overcome this limitation. These configurations are vendor-specific, so the SharePoint Product Group did not test them.
We do not offer end-to-end support for the kinds of configurations that are described in the "Introduction" section. We require users to eliminate the third-party component as a cause of the problem before we provide support. In certain cases, the customer would have to show a reproduction of the problem in a co-located environment.
Notes and caveats:
All active Servers in a farm should have a maximum of 1 millisecond latency to the SQL Server that serves them.
Planning and Monitoring SQL Server Storage for Office SharePoint Server: Performance Recommendations and Best Practices (white paper)
The following is the Microsoft general support policy when third-party clustering tools are involved:
"If you cluster SQL Server with any clustering product other than Microsoft Server Clustering, your primary support contact is the third-party cluster solution provider for any support issues that are related to SQL Server. SQL Server was developed and tested by using Microsoft Server Clustering. Third-party clustering solutions that support SQL Server installations should be your primary contact for any installation issues, performance issues, or cluster behavior issues. CSS provides commercially reasonable support for third-party cluster installations in the same manner that we do for a stand-alone version of SQL Server."
327518 The Microsoft SQL Server support policy for Microsoft Clustering
814607 Microsoft support for server clusters with third-party system components
Additional resources and recommended SharePoint topologies are available on the TechNet Center.
Backup, Recovery, and Availability Resource Center for SharePoint Server 2007
Microsoft Windows SharePoint Services 3.0, Microsoft Office SharePoint Server 2007, Microsoft SharePoint Foundation 2010, Microsoft SharePoint Server 2010, Microsoft SharePoint Foundation 2013, Microsoft SharePoint Server 2013