VMware KB 1024051
High availability for VMware vCenter Server can be primarily implemented using VMware vCenter Server Heartbeat, VMware High Availability (HA), and Fault Domain Manager (FDM) for vCenter Server 5.x. While VMware vCenter Server Heartbeat provides deep and comprehensive levels of protection against unplanned and, in some cases, planned vCenter Server downtime, VMware HA/FDM is a good alternative for vCenter Server instances running on a virtual machine. VMware HA/FDM provides robust general-purpose protection against hardware and OS failures.
You may choose to protect VMware vCenter Server using third-party clustering solutions including, but not limited to, MSCS (Microsoft Cluster Services) and VCS (Veritas Cluster Services). VMware does not certify these third-party solutions. VMware will offer best effort support for any issues encountered with an environment that uses third-party solutions for protecting against VMware VirtualCenter downtime. However, if your issue is determined to be related to the third-party clustering solution, VMware will refer to our third-party software policy