vSphere 5 introduces a new High Availability agent named FDM.
read all the article "vSphere 5 – New High Availability Agent Introduced – FDM" (from vladan.fr) and have a look at Eric Sloof video presentation
[...] There is no more AAM agent like in vSphere 4.1. Instead, there has been a new agent introduced which is named FDM – Fault Domain Manager. The Primary/Secondary concept with 5 primary nodes which has been known in vSphere 4, is gone. You no longer needs to worry not to loose all those 5 primary nodes at the same time …. and loose the HA functionality for the rest of the cluster. Now there is only one agent in the cluster which plays the role of Master. The agent is called FDM – Fault Domain Manager. One host takes the role of Master. The other agents on other hosts plays only roles as a Slaves, and can became Masters in case the master fails. [...]
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