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HA: Vmware runs a heart beat between all its hosts, when any host misses a heart beat for a specified amount of time or specified number of times vmware moves all the VM's running on the host to different hosts on the cluster. This is a cold fail over since the host is rebooted. But the host keeps it identity on the network and all databases on the host will come up transparently. This happens withing minutes.
DRS: This mechanism tries to keep all hosts in the cluster equally busy. If a host crosses a threshold on utilization vmware automatically moves some VM's to different hosts. This move it completely online and transparent to the application.
VMOTION: The db host can also be manually vmotioned to a different host completely online. This is done if the VM team needs to do some maintenance on host running the db host. ase
Database HA:
There is no HA mechanism built in the infrastructure for database HA. If a database instance or database fails, the monitoring tool will inform the operators about the failure, operators would then call the on call dba who will gauge the failure and take appropriate action. It's difficult to come with a time range for this action since it could vary based on type of failure. The options range from just restarting the instance to doing a database recovery from snapshot to getting storage and systems team involved.