Calculation of vSAN capacity utilization alarm 'What if the most consumed host fails'

Products

• VMware vSAN

Issue/Introduction

Alarm of "Capacity Utilization Health – Disk Space check in the vSAN Health Service"

Environment

VMware vSAN 7.0.x

VMware vSAN 8.0.x

 

Cause

 

 Configuration of vSAN cluster

The vSAN cluster formed by 4 nodes, which contains 2 x 32 GB capacity disks. The capacity of the vsanDatastore is 256 GB.

From the UI, the capacity of the vSAN is 255.46 GB. There are 177.87 GB used. The live usage is 177.97/255.46 = 69.67%.

Resolution

When the most consumed host failed, esx-03 in this case.

'What if the most consumed host fails' predicts how the vSAN cluster will behave from the storage and component utilization perspective after most consumed host fails.

When the alarm triggerred, you can verify detail info by click TROUBLESHOOT

 

vSAN datastore will loss esx-03's capacity which is approximate 64 GB. The remain capacity of vsanDatastore is 191.6 GB. And vSAN will rebuild the components resides on original esx-03, so the Used capacity still remains at approximate 177.93 GB.

The usage of vSAN datastore is 177.93/191.6  = 92.86%, which triggered the alarm "What if the most consumed host fails".

Additional Information

https://knowledge.broadcom.com/external/article/327052/vsan-health-service-limits-health-afte.html