6.0.1

The default settings for monitoring sensitivity are described in Table 2-1. You can also specify custom values
for both monitoring sensitivity and the I/O stats interval by selecting the Custom checkbox.
Table 2‑1. VM Monitoring Settings
Setting Failure Interval (seconds) Reset Period
High 30 1 hour
Medium 60 24 hours
Low 120 7 days
After failures are detected, vSphere HA resets virtual machines. The reset ensures that services remain
available. To avoid resetting virtual machines repeatedly for nontransient errors, by default, virtual
machines will be reset only three times during a certain configurable time interval. After virtual machines
have been reset three times, vSphere HA makes no further attempts to reset the virtual machines after
subsequent failures until after the specified time has elapsed. You can configure the number of resets using
the Maximum per-VM resets custom setting.
NOTE The reset statistics are cleared when a virtual machine is powered off then back on, or when it is
migrated using vMotion to another host. This causes the guest operating system to reboot, but is not the
same as a 'restart' in which the power state of the virtual machine is changed.
If a virtual machine has a datastore accessibility failure (either All Paths Down or Permanent Device Loss),
the VM Monitoring service suspends resetting it until the failure has been addressed.
VM Component Protection
If VM Component Protection (VMCP) is enabled, vSphere HA can detect datastore accessibility failures and
provide automated recovery for affected virtual machines.
VMCP provides protection against datastore accessibility failures that can affect a virtual machine running
on a host in a vSphere HA cluster. When a datastore accessibility failure occurs, the affected host can no
longer access the storage path for a specific datastore. You can determine the response that vSphere HA will
make to such a failure, ranging from the creation of event alarms to virtual machine restarts on other hosts.
NOTE When you use the VM Component Protection feature, your ESXi hosts must be version 6.0 or higher.
Types of Failure
There are two types of datastore accessibility failure:
PDL
PDL (Permanent Device Loss) is an unrecoverable loss of accessibility that
occurs when a storage device reports the datastore is no longer accessible by
the host. This condition cannot be reverted without powering off virtual
machines.
APD
APD (All Paths Down) represents a transient or unknown accessibility loss
or any other unidentified delay in I/O processing. This type of accessibility
issue is recoverable.
Chapter 2 Creating and Using vSphere HA Clusters
VMware, Inc. 19