If VM Component Protection (VMCP) is enabled, vSphere HA can detect datastore accessibility failures and provide automated recovery for affected virtual machines.
Types of Failure
- 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 (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.
VM Component Protection is configured in the vSphere Client. Go to the Configure tab and click vSphere Availability and Edit. Under Failures and Responses you can select Datastore with PDL or Datastore with APD. The storage protection levels you can choose and the virtual machine remediation actions available differ depending on the type of database accessibility failure.
- PDL Failures
- Under Datastore with PDL, you can select Issue events or Power off and restart VMs.
- APD Failures
The response to APD events is more complex and accordingly the configuration is more fine-grained. You can select Issue events, Power off and restart VMs--conservative restart policy, or Power off and restart VMs--aggressive restart policy