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

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

vSAN supports two types of failure states for components:

Table 1. Failure States of Components in vSAN

Component Failure State

Description

Recovery

Cause

Degraded

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

vSAN 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 vSAN detects a temporary component failure where the component might recover and restore its working state.

vSAN starts rebuilding absent components if they are not available within a certain time interval. By default, vSAN 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