Putting a host into maintenance mode causes reduced availability vSAN object alarms on a vSAN cluster

Products

• VMware vSAN

Issue/Introduction

Getting reduced availability messages when putting a host in maintenance mode with ensure accessibility while upgrading the vSAN cluster.

 

 

Environment

VMware vSAN (All Versions)

Cause

vSAN Skyline Health alarms in vCenter become active when the host is in maintenance mode.  In a two node stretch cluster or three node standard cluster during a cluster upgrade it's normal for object to go into a reduced availability state as there are not enough fault domains to meet storage policy compliance.  This means that during the time that a host is in maintenance mode, the reduced availability objects alarm will be active.  If in a four node or larger cluster and using ensure accessibility, the reduced availability alarm will also be active.  In these situations, the vSAN may attempt to move component data to the available node after the 60 minute delay timer.  If there are delays in the host maintenance, the timer can be extended to avoid an unnecessary resync.

Changing the default repair delay time for a host failure in vSAN

Resolution

Continue with the host maintenance as these reduced availability alarms are normal.  Anytime a vSAN node is unavailable to the vSAN (maintenance mode, host crash, disk failure), the objects that have a component on that host will go into a reduced availability state.  For additional information on the maintenance mode operation in vSAN, see Place a Member of vSAN Cluster in Maintenance Mode