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Thursday, 26 July 2012

Advanced Configuration options for VMware High Availability

Purpose

In the majority of environments, VMware High Availability (HA) default settings do not need to be changed. However, depending on your specific environment you may need to modify some HA options. This article describes the different configuration options available and how to apply them.

Resolution


Note: Not all configuration variables work in all versions of VirtualCenter/vCenter Server. As new variables are introduced in newer releases, they remain throughout later versions.

Applying a VMware HA customization

To access the various customizations available:
  1. Login to vCenter Server with VMware Infrastructure/vSphere Client as an administrator.
  2. Right-click the Cluster in the Inventory and select Edit Settings.
  3. Click VMware HA.
  4. Click the Advanced Options button.
  5. Enter Option and Value fields as appropriate (see below).
  6. Click OK.
  7. Click OK again.
  8. Wait for the Reconfigure Cluster task to complete and then right-click the Cluster again from the Inventory.
  9. Click Properties.
  10. Disable VMware HA and wait for the Reconfiguration Cluster task(s) to complete.
  11. Right-click the cluster and Enable VMware HA to have the settings take effect.

VMware High Availability Advanced options

These settings are available in VirtualCenter 2.0.0 and above:
  • das.defaultfailoverhost = <hostname>This option/value pair is used to set a preferred failover host, where <hostname> represents the short name of the preferred host. The host specified is used as the first choice in case of a failure. However, if there is insufficient capacity VMware HA automatically selects an alternate host.
  • das.isolationaddress = <value>This option/value pair changes the default isolation address, where <value> represents the IP address that is to be used as the isolation address. By default the address used is the Default Gateway address for the ESX host because it is a highly available address. This address is queried as one of the items in determining if an isolation response has occurred on the host, thus if this parameter is changed be sure to use a reliable, highly available IP address with as few failure points between it and the ESX host as possible.
These settings are available in VirtualCenter 2.x and above:
  • das.failuredetectiontime = <value>This option/value pair changes the default failure detection timeout, where <value> represents the failure time in milliseconds. VMware HA uses this timeout in declaring an isolation response, and does not declare a host as isolated until this timeout has been reached without any heartbeats received. By default the default failure detection time is 15 seconds (15000 ms). However, another common alternative is 60 seconds (60000 ms).

    Note: das.failuredetectiontime is no longer supported in vCenter Server 5.x. 

  • das.usedefaultisolationaddress = <value> 

    This option/value pair disables the use of the default gateway as an isolation address, where <value> is either true or false. By default this value is set to true. This parameter is generally used in conjunction with thedas.isolationaddress1 to das.isolationaddress10 parameter(s) listed below.
  • das.isolationaddress1 to das.isolationaddress10 = <value>These option/value pair(s) specify more than one alternate isolation address for VMware HA to use, where<value> represents the IP address to be used for isolation detection. When using more than one isolation address it is recommended that the das.failuredetectiontime parameter be increased to ensure proper failover detection can occur. Also, although up to 10 different isolation addresses can be specified one or two addresses should be sufficient for proper failover detection. For more information on setting multiple isolation addresses, see Setting Multiple Isolation Response Addresses for VMware High Availability (1002117).

    Note: The 
    das.isolationaddress parameter is still supported if you are not using more than one alternative isolation address.
These settings are available in VirtualCenter 2.5.0 and above:
  • das.powerOffOnIsolation = <value>

    T
    his option/value pair overrides the default isolation response setting to shutdown all the virtual machines when an isolation response occurs, where <value> is either true or false. By default this value is set to true. If changed to false all virtual machines will remain powered on in case of isolation.
  • das.vmMemoryMinMB = <value>

    T
    his option/value pair overrides the default memory slot size value used for admission control for VMware HA, where <value> is the amount of RAM in MB to be used for the calculation if there are no larger memory reservations. By default this value is set to 256MB.
  • das.vmCpuMinMHz = <value>This option/value pair overrides the default CPU slot size value used for admission control for VMware HA, where<value> is the amount of CPU in MHz to be used for the calculation if there are no larger CPU reservations. By default this value is set to 256MHz.
These settings are available in VirtualCenter 2.5.0 Update 2 and above:
  • das.conservativeCpuSlot = <value>

    This option/value pair reverts how conservative VMware HA is in regards to vCPU when calculating slot size for admission control, where <value> represents either a value of true or false. By default in VirtualCenter 2.5.0 Update 2 this option is false to make the admission control less conservative. If set to true it reverts to the behavior of admission control as it was VirtualCenter 2.5.0, and VirtualCenter 2.5.0 Update 1.
  • das.allowvMotionNetworks = <value>

    This option/value pair allows vMotion networks to be considered for VMware HA usage, where <value> represents a value of true or false. This parameter enables a host that only has one Network card configured for management and vMotion combined to be properly configured for VMware HA. By default this value is false, and any vMotion network is ignored.
  • das.allowNetwork[...]

    This option enables the use of port group names to control the networks used for HA. You can set the value to be "Service Console 2" or "Management Network" to use those port group names in the networking configuration.
This setting is available in VirtualCenter 2.5.0 Update 3 and above:
  • das.ignoreRedundantNetWarning = <value>
    To suppress the message Host <xxx> currently has no management network redundancy, which appears if the Service Console does not have network redundancy configured properly on ESX hosts in the VMware High Availability (HA) cluster or if the warning appears for a host already configured in a cluster, set the VMware HA advanced option das.ignoreRedundantNetWarning to true and reconfigure VMware HA on that host. For further information, see KB 1004700.
This setting is available in vCenter Server 4.x and above:
  • das.slotmeminmb

    This option defines the maximum bound on the memory slot size. If this option is used, the slot size is the smaller of this value or the maximum memory reservation plus memory overhead of any powered-on virtual machine in the cluster. 
  • das.slotcpuinmhz

    This option defines the maximum bound on the memory slot size. If this option is used, the slot size is the smaller of this value or the maximum memory reservation plus memory overhead of any powered-on virtual machine in the cluster. 
These settings are available in vCenter Server 5.0
  • das.ignoreinsufficienthbdatastore 
Disables configuration issues created if the host does not have sufficient heartbeat datastores for vSphere HA. Default value is false.
  • das.heartbeatdsperhost 
Changes the number of heartbeat datastores required. Valid values can range from 2-5 and the default is 2.
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