Comparing VMware HA 4.x and vSphere HA 5.x
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Comparing VMware HA 4.x and vSphere HA 5.x


Article ID: 338778


Updated On:


VMware vCenter Server


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


VMware vCenter Server 5.1.x
VMware vCenter Server 5.0.x


VMware HA 4.x
vSphere HA 5.x
VMware HA in vSphere 4.x has AAM (Automated Availability Manager) agents
VMware HA in vSphere 5.x 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 primary host or a secondary host. Only one primary host exists per cluster and all other hosts are secondary hosts. If the primary host fails, is shut down, or is removed from the cluster a new election is held.
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
Primary Host:
  • Monitors the state of secondary hosts. If a secondary 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
  • Primary/secondary Host management network is lost.
  • Primary host management network lost & cannot ping isolation response IP address.
  • Primary 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.cfgincludes settings for logging, alerting and the working FDM directory.
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