This paper is intended to clarify concepts involved with choosing solutions for vSphere site availability, and to help understand the use cases for availability solutions for the virtualized infrastructure. Specific guidance is given around the intended use of DR solutions like VMware vCenter Site Recovery Manager and contrasted with the intended use of geographically stretched clusters spanning multiple datacenters. While both solutions excel at their primary use case, their strengths lie in different areas which are explored within.
The purpose of this paper is to clarify some of the concepts involved with vSphere site availability, and to help understand the use cases for these availability solutions in the vSphere landscape. The intent is to provide guidance not in terms of purchasing decisions or products, but in terms of what various technologies intend to do and how to best achieve availability goals for your environment.
When designing for availability, in many instances the solution architect will have to choose between these technologies. Stretched clusters are incompatible with Site Recovery Manager and therefore, the architect is faced with a decision whether to choose active non-disruptive site balancing with unmanaged crash recovery via a stretched cluster or choose a robust disaster recovery solution that will restart failed services in a controlled and known fashion but is predicated on service outage.