vSAN -- Skyline Health -- Resync Operations Throttling
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vSAN -- Skyline Health -- Resync Operations Throttling

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Article ID: 326963

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Updated On:

Products

VMware vSAN

Issue/Introduction

If the Health Check fails, it indicates that the Host(s) listed under "Hosts with resync operation throttled"
have the resynchronization bandwidth limit set to a specified value
and shows an error when the value is less than 20 Mbps.
As a result, Resync operations might be slow. 

Under vCenter Versions 6.5 & 6.7, it was possible to configure a bandwidth limit for Resync operations in the Web Client
Throttle Resynchronization Activity in the vSAN Cluster )

The manual throttle of Resync has outlined above, has been deprecated with Version 7.0, due to the introduction of Adaptive Resync.
"vSAN 6.7 and newer contains a sophisticated method to balance the use of resources during times of resynchronization activities.
Adaptive Resynchronization, or Adaptive Resync, optimizes vSAN’s ability to dynamically,
and transparently adapt I/O to best accommodate the needs of the virtual machines (VMs)
against the tasks of the underlying storage system.  
This feature requires no manual configuration or intervention."

( Reference: Adaptive Resync in vSAN )

 


Environment

VMware vSAN 6.5.x
VMware vSAN 8.0.x
VMware vSAN 7.0.x
VMware vSAN 6.7.x

Resolution

Due to the introduction of Adaptive Resync, it is recommended to disable any manual configured Bandwidth Limitations
unless these limitations are needed for particular cases like significant Resync traffic causing high VM latencies. 

In order to resolve the Warning "Resync Operations Throttling", the Resync Throttling needs to be manually disabled on the Hosts
which are showing under "Hosts with resync operation throttled", 
by logging into the Host via SSH/Putty and run the following command:
esxcfg-advcfg -s 0 /VSAN/DomCompResyncThrottle

Verify your change by running the following command:
esxcfg-advcfg -g /VSAN/DomCompResyncThrottle

The output should show:
Value of DomCompResyncThrottle is 0

Alternative:
Configuring resync throttle on a vSAN cluster via PowerCLI (83742)