When upgrading ESXi in a vSAN Cluster, resyncing objects is taking too long

Products

• VMware vSAN

Issue/Introduction

Once a host is placed into maintenance mode with Ensure accessibility. It is noted that objects then enter a "reduced availability with no rebuild - Delay Timer" state.

Cluster -> Monitor -> vSAN -> Skyline Health 

 

Environment

vSAN 7.0

vSAN 8.0

Cause

Objects go into health state :"reduced availability with no rebuild - Delay Timer"

This is expected, as some components are now absent due to placing the host into maintenance mode but the overall objects are still accessible.

Note here the status also states "Delay Timer" this means vSAN waits before rebuilding a disk object after a host is either in a failed state or in Maintenance Mode.

By default, the repair delay value is set to 60 minutes; this means that in the event of a host failure, vSAN waits 60 minutes before rebuilding any disk objects located on that particular host.

This is because vSAN is not certain if the failure is transient or permanent.

Resolution

This is expected behavior when placing the host into Maintenance mode with ensure accessibility as components are absent and the delay timer has yet to take effect.

 

If the user then chooses to repair the objects immediately. This option will resynchronize the absent objects on available hosts in the vSAN cluster.

This is expected and can create a large resync depending on the amount of absent components that need to be rebuilt. 

 

Additional Information

Please see below for more details on the rebuild delay timer and vSAN Rebuilds and Repairs.

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

Understanding vSAN Rebuilds and Repairs