Comparing VMware HA 4.x and vSphere HA 5.0

Purpose

This article provides a detailed comparison of VMware High Availability (HA) 4.x and vSphere HA 5.x.

Resolution

Capability	VMware HA 4.x	vSphere HA 5.0
Agents	VMware HA in vSphere 4.x has AAM (Automated Availability Manager) agents	VMware HA in vSphere 5.0 has FDM (Fault Domain Manager) agents installed
Cluster Members	The first five hosts added to the cluster are designated as primary hosts, and all subsequent hosts are designated as secondary hosts. If a primary host is removed from the cluster, VMware HA promotes another (secondary) host to primary status.	Each host in the cluster functions as a master host or a slave host. Only one master host exists per cluster and all other hosts are slave hosts. If the master host fails, is shut down, or is removed from the cluster a new election is held.
Responsibilities	Primary Hosts: Decide where to restart virtual machines. Keep track of failed restart attempts. Determine when it is appropriate to keep trying to restart a virtual machine	Master Host: Monitors the state of slave hosts. If a slave host fails or becomes unreachable, the virtual machines on that host are restarted. Monitors the power state of all protected virtual machines. Manages the lists of cluster hosts and protected virtual machines. Acts as vCenter Server management interface to the cluster and reports the cluster health state.
Host isolation methods	Isolation is based on network only.	Isolation is based on network and storage.
Host Failure Detection	If a host stops receiving heartbeats from all other hosts in the cluster and isolation address for 15 seconds or longer	Master/Slave Host management network is lost. Master host management network lost & cannot ping isolation response IP address. Master host fails.
Slot Size Calculation	The default CPU reservation of each powered-on virtual machine is 256 Mhz.	The default CPU reservation of each powered-on virtual machine is 32 Mhz.
Configuration Files	There are no configuration files for VMware HA.	The configuration file is located at/etc/opt/vmware/fdm/ fdm.cfg includes settings for logging, alerting and the working FDM directory.
Logs	Logs are available in/var/log/vmware/aam	The log file is located in/var/log/vmware/fdm/  FDM uses a single log file per host and supports syslog integration.  The remaining files are located at/etc/opt/vmware/fdm/  hostlist: Includes hostnames, IP Addresses, MAC addresses and heartbeat datastores of hosts participating in the cluster.  compatlist: A compatibility matrix which lists all the hosts with which a Virtual Machine is compatible.  clusterconfig: Includes details such as Host Isolation Response, VM Restart Priority, Admission Controls & any relevant DRS & DPM information.
Heartbeat Datastores	Not available	Datastores are used as a communication channel only when the management network is lost, such as in the case of isolation & network partitioning.

Source:-
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2004401