In case you'll want to get into stretched clustering, get deep info and recommended practices, know that you might want to check this whitepaper from VMware which discusses just that. This paper was updated to stay current with vSphere 6.0 as the previous version written back in 2012 got slightly outdated.
When thinking about stretched cluster architecture, one must first take into account a hardware compatibility, supported latency for synchronous storage replication links, supported latency for management networks or supported throughput for vMotion network. Additionally, the single storage subsystem must be able to span both sites, and so the datastore must be accessible (in RW) from both sites simultaneously. Such architecture needs very low latency and good bandwidth. The details what's supported in vSphere 6.0 are in this paper, which is considered as a reference when it comes to stretched cluster architecture.
VMware vSphere Metro Storage Cluster (vMSC) is a specific configuration within the VMware Hardware Compatibility List (HCL). These configurations are commonly referred to as stretched storage clusters or metro storage clusters and are implemented in environments where disaster and downtime avoidance is a key requirement. This best practices document was developed to provide additional insight and information for operation of a vMSC infrastructure in conjunction with VMware vSphere. This paper explains how vSphere handles specific failure scenarios, and it discusses various design considerations and operational procedures.
There are Two types of configuration depending of how the hosts are accessing the storage:
Uniform – ESXi hosts are connected from both sites to a storage node in the storage cluster across all sites. Patch to the hosts are stretched across a distance.
Nonuniform – hosts in data center A have access only to the array within the local data center, not to the remote datacenter. It's the array who has….
The paper goes quite in details concerning the whole architecture and implementation. Screenshot from the paper…
The paper is available at this page: