vSAN -- Citrix VDI Virtual Machines experiencing significant Performance degradation, impacting normal operations and User experience

Products

• VMware vSAN
• VMware vSAN 7.x
• VMware vSAN 8.x

Issue/Introduction

During patching of a large amount of Citrix VDI Machines located on a healthy vSAN Cluster, the following is observed:

• Users experiencing Performance degradation when using the affected VMs. VMs might hang or slow responding
• Via the Cluster Performance Graphs in the vSphere Client, Spikes are observed in one or more Categories. The Spikes started to occur at the time the Patching started. 

Example Screenshot showing vSAN Cluster Performance Graphs:

 

After completion of the Patching, the Performance degradation went away and no further spikes were observed.

Citrix VDI is implemented on the System according to Best Practices ( if unsure, please open Ticket with Citrix Vendor ) 

Environment

vSAN 7.x

vSAN 8.x

Cause

If the Performance degradation only existed during the Patching and vSAN Cluster is otherwise considered as fully healthy:

Patching of a large amount of VMs within a short amount of time causes an increased I/O load on the affected vSAN Cluster,

potentially resulting in some Spikes and temporary Congestion on vSAN.

 

 

Resolution

A.) Consider to stagger the Patching of the VMs to distribute load on vSAN more evenly

B.) Evaluate enabling of Large Cache Tier Support

 

If assistance is required, please open a Ticket with VMware by Broadcom Support.