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Systems & Data Center · Intermediate

vSphere High Availability (vSphere HA)

A cluster feature that automatically restarts VMs on surviving ESXi hosts after a host failure.

Definition

HA uses a primary host that monitors others through network heartbeats and datastore heartbeats. Admission control reserves capacity for failover. VMs restart, so there is a brief outage. VM monitoring can also restart unresponsive guests.

Example

When host esx03 loses power, its 20 VMs restart on the remaining hosts within minutes.

Exam tip

HA restarts VMs (some downtime); Fault Tolerance provides zero downtime with a running secondary.

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