Understanding vSphere Availability and DRS

High Availability protects from down time by automating recovery in the event of a host failure. Distributed Resource Scheduler (DRS) ensures performance by balancing virtual machine workloads across hosts a cluster.

vSphere Availability provides high availability for virtual machines by pooling the virtual machines and the hosts they reside on into a cluster. Hosts in the cluster are monitored and in the event of failure, the VM’s on the failed host are restarted on the alternate hosts.

In a vSphere Availability cluster, a single host is automatically elected as the master host. The master host then communicates with vCenter server and monitors the state of all protected VM’s and of the slave hosts. Different types of host failures are possible and master host uses network and datastore heartbeating to determine the type of failure.

Note :- vSphere Availability is a host function and there is no dependency on vCenter to effectively fail over VMs to other hosts in the cluster.


Enable and Configure vSphere Availability

  1. Click “Cluster Site A”
  2. Click “Actions” and “Settings


  1. Click “vSphere Availability” and click “Edit” marked in Yellow


  1. Check the box “Turn ON vSphere HA

Note :- ‘Turn on Proactive HA’ will proactively migrate VMs from host that has degrading hardware


Failures and Responses 

  1. By selecting VM and Application Monitoring, a VM will be restarted if heartbeats are not received within a set of time, by default 30 seconds


Admission Control 

  1. We are setting aside a certain percentage of CPU and Memory resources to be used for failover, in the above below case I selected 25% for each


Heartbeat Datastores

  1. Datastore heart beating allows vSphere HA to monitor hosts when a management network partition occurs and to continue to respond to failures that occur.
  2. Select “Automatically Select datastores accessible from the host


Next we will move on to DRS

Enable and Configure DRS

  1. Click “Configuration” and click “vSphere DRS”
  2. Click Edit which is marked in Yellow


  1. Check “Turn ON vSphere DRS” and select “Fully Automated


Here i have selected Fully Automated but please the below description on the levels


Hope this was informative to you all. Thanks for reading and share your thoughts in twitter @shaan4me

















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