In Virtual SAN, components that have failed can be in absent or degraded state. According to the component state, Virtual SAN uses different approaches for recovering virtual machine data.

Virtual SAN also provides alerts about the type of component failure. See Using the VMkernel Observations for Creating Alarms and Using the Virtual SAN Default Alarms.

Virtual SAN supports two types of failure states for components:

Table 1. Failure States of Components in Virtual SAN

Component Failure State

Description

Recovery

Cause

Degraded

A component is in degraded state if Virtual SAN detects a permanent component failure and assumes that the component is not going to recover to working state.

Virtual SAN starts rebuilding the affected components immediately.

  • Failure of a flash caching device

  • Magnetic or flash capacity device failure

  • Storage controller failure

Absent

A component is in absent state if Virtual SAN detects a temporary component failure where the component might recover and restore its working state.

Virtual SAN starts rebuilding absent components if they are not available within certain timeout. By default, Virtual SAN starts rebuilding absent components after 60 minutes.

  • Lost network connectivity

  • Failure of a physical network adapter

  • ESXi host failure

  • Unplugged flash caching device

  • Unplugged magnetic disk or flash capacity device