Datastore with APD

In many failure scenarios, ESXi cannot determine if it has lost access to a volume permanently (e.g. volume removed) or temporarily (e.g. network outage). In the case where there is a failure that ESXi cannot communicate to the underlying array, the array cannot send the appropriate SCSI sense codes and ESXi is unable to determine the type of loss. This state is referred to as All Paths Down (APD).

If a failure occurs, there is a timeout of 140 seconds and then ESXi considers the volume APD. Once this occurs all non-virtual machine I/O to the storage volume is terminated, but virtual machine I/O is still indefinitely retried. ESXi 6.0 introduced the ability for vSphere HA to respond to this situation.

APD response options:

• All Paths Down (APD) Failure Response: by default, vSphere HA does nothing in the face of APD. Everpure recommends setting this option to either Power off and restart VMs – Conservative restart policy or Power off and restart VMs – Aggressive restart policy. The conservative option will only power-off VMs if it is sure that they can be restarted elsewhere. The aggressive option will shut them down regardless and best effort try to restart them elsewhere. Everpure has no specific recommendation for either and it is up to the customer to decide. Everpure does recommend choosing one of the two Power off options and not leaving it Disabled or set to Issue Events.
• Response recovery: by default, if an APD situation recovers before a power-off has occurred, ESXi will do nothing. In some cases, it might be preferable to have the VMs restarted after a prolonged APD occurrence as some applications and operating systems do not respond well to a lengthy storage outage. In this case, vSphere HA can react to the temporary loss and subsequent recovery of storage by resetting the affected virtual machines. Everpure has no specific recommendations on this setting.