Hello,
first some informations about HA. The vSphere HA can protect any VM (or most of them) which also include vCenter (Windows or VCSA). The vCenter is needed for enabling and configure vSphere HA but its not needed for HA kicking in when a failure occurs. If a Host goes down which also runs vCenter VM its the job of the HA Master to manage the restart of the VMs on other Hosts.
But there might be a requirement for a vCenter with up to 99.99% availability if you run a VMware VIEW environment or vCD for example.
- I thought that a MSSQL server can only support a single vCenter and its not possible that 2 independend vCenter share the same MSSQL
- With vSphere 6.0 it should be supportet that a vCenter can use a MSSQL Cluster for the SQL Backend. But that doesnt protect the VPXD and the other vCenter services
- I think there also comes support to run vCenter in a MS Failover Cluster. But its not very common because the future of vCenter is the linux based VA and not the windows version. Check
http://kb.vmware.com/kb/1024051
In the old vSphere 4.0-5.5 there was "vCenter Heartbeat" as extra product to realize high availability vCenter.
Regards,
Joerg