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HA Advanced Options

  • das.failuredetectiontime – This setting was introduced in VirtualCenter 2.0.2 to allow the default interval for HA detection to be changed. Previously this was hard-coded so that if a host did not respond in 15 seconds then it would be considered failed. This setting is in milliseconds and can be changed from the default of 15000 milliseconds. For example if you wanted to increase this to 60 seconds you would set it to 60000 milliseconds (don’t use commas in the number).
  • das.poweroffonisolation – This setting is the default cluster setting for virtual machine isolation response that is set through the VI Client. The default is true which powers off virtual machines in case of an HA event. Setting this to false leaves the virtual machine still running on the isolated host when an HA event occurs.
  • das.isolationaddress – This setting was introduced in VirtualCenter 2.0.2 and is the IP address that HA will ping to determine if a host is isolated from the network. If this option is not specified, the default gateway of the console network is used. This default gateway has to be some reliable address that is known to be available, so that the host can determine if it is isolated from the network. Using multiple isolation response addresses gives HA a potentially more accurate picture of the network connectivity of a host. There may be situations in which a single isolation address would indicate that a host is in a state of complete isolation from the network, but access to additional isolation addresses would show that only a partial network failure has occurred. You can have a total of 10 isolation addresses set using the following format das.isolationaddressX, where X is a number 1-10. If you use this setting you should change the default failure detection time (das.failuredetectiontime ) to 20 seconds or greater. In general the more isolation response addresses configured, the longer you should make the timeout to ensure that proper failure detection can occur.
  • das.usedefaultisolationaddress – By default, HA uses the default gateway of the console network as an isolation address. This attribute specifies whether that should be used or not, the values are true or false. If you are using the das.isolationaddress setting then this should be set to false.
  • das.isolationShutdownTimeout – The amount of time that HA waits to gracefully shutdown a VM if the “Shutdown VM” option is selected for isolation response. The default is 300 seconds.
  • das.defaultfailoverhost – If this is set, HA will first try to fail over hosts to the host specified by this option. This is useful if you want to utilize one host as a spare failover host, but is not usually recommended, because HA tries to utilize all available spare capacity among all hosts in the cluster. If the specified host does not have enough spare capacity, VMware HA tries to fail over the virtual machine to any other host in the cluster that has enough capacity.
  • das.failuredetectioninverval – This setting was introduced in vCenter Server 2.5 Update 2 and is the interval that is used for heartbeat detection amongst ESX hosts. The default is that a host will check for a heartbeat every second (1000 milliseconds), you may want to increase this if your hosts are on remote or high latency networks.
  • das.allowVmotionNetworks – This setting was introduced in vCenter Server 2.5 Update 2 specifically for ESXi which does not utilize a vswif service console network like ESX hosts and instead uses a special management network and will allow a NIC that is used for VMotion networks to be used for HA also. This is to allow a host that has only has a single NIC configured for the both the service console and VMotion combined to be used for HA; by default VMotion networks are ignored.
  • das.allowNetwork – This setting was introduced in vCenter Server 2.5 Update 2 and allows the use of port group names to control the networks used for HA. Starting with vCenter Server 2.5 Update 2, HA has an enhanced network compliance check to increase cluster reliability. This enhanced network compliance check helps to ensure correct cluster-wide heartbeat network paths. This also helps prevent delayed failure detection and “Split Brain” conditions in certain scenarios. When configured, the HA cluster only uses the specified networks for HA communication. You can set the value to be “Service Console 2″ or “Management Network” to use the networks associated with those port group names in the networking configuration. You can set this using the following format, das.allowNetworkX where X is a number starting with 0, i.e. das.allowNetwork0 = “Service Console” or daas.allowNetwork1 = “Service Console 2″. More detail on this setting can be found in the following VMware KB articles: http://kb.vmware.com/kb/1006606 and http://kb.vmware.com/kb/1006541
  • das.vmMemoryMinMB – Specifies the minimum amount of memory (in megabytes) sufficient for any virtual machine in the cluster to be usable. This value is used only if the memory reservation is not specified for the virtual machine and is used for HA admission control and calculating the current failover level. If no value is specified, the default is 256MB, reducing this can help prevent the warning about insufficient resources and the red exclamation mark that indicates a cluster does not have sufficient failover capacity.
  • das.vmCpuMinMHz – Specifies the minimum amount of CPU (in megahertz) sufficient for any virtual machine in the cluster to be usable. This value is used only if the CPU reservation is not specified for the virtual machine and is used for HA admission control and calculating the current failover level. If no value is specified, the default is 256MHz, reducing this can help prevent the warning about insufficient resources and the red exclamation mark that indicates a cluster does not have sufficient failover capacity.
  • das.bypassNetCompatCheck – This setting was introduced in vCenter Server Update 3 to provide the ability to disable the HA enhanced network compliance check that was introduced in vCenter Server 2.5 Update 2. The enhanced network compliance check helps to ensure correct cluster-wide heartbeat network paths. This setting allows you to bypass this check to prevent HA configuration problems. To bypass the check, add das.bypassNetCompatCheck=true to the HA advanced settings.
  • das.iostatsInterval – Used for virtual machine monitoring, occasionally virtual machines that are still functioning properly stop sending heart-beats. To avoid unnecessarily resetting such virtual machines, the VM Monitoring service also monitors a virtual machine’s I/O activity. If no heartbeats are received within the failure interval, the I/O stats interval (a cluster-level attribute) is checked. The I/O stats interval determines if any disk or network activity has occurred for the virtual machine during the previous two minutes (120 seconds). If not, the virtual machine is reset. This default value (120 seconds) can be changed using this setting.

To configure HA with any of these advanced settings just follow the below steps:

  1. Select your cluster in the VI Client and right-click on it and select “Edit Settings”.
  2. Select VMware HA in the left hand pane.
  3. In the right hand pane click the “Advanced Options” button.
  4. When the Advanced Options window is display double-click on one of the blank fields under the Options column to edit it.
  5. Enter an option name (i.e. das.failuredetectiontime) and hit Enter.
  6. Double-click on the field next to it in the Value column and edit a value (i.e. 60000) and hit Enter.
  7. Repeat this procedure for any additional options that you want to add and click the OK button.