Identify Path Selection policy type for round robin (Latency Based / IOPS )

Products

• VMware vSphere ESXi

Issue/Introduction

• This article is created to identify if the storage path selection policy type is set to Latency or IOPS.

  • VMware Path Selection policy :  VMW_PSP_RR - Round Robin (VMware) :

  Round Robin is the default policy for many arrays. It uses an automatic path selection algorithm rotating through the configured paths.

  The latency mechanism that can be activated for the policy makes it more adaptive. To achieve better load balancing results, the mechanism dynamically selects an optimal path by considering the following path characteristics:

1. 1. 1. I/O bandwidth [IOPS]

         • Selects paths based on the number of I/O operations per second (IOPS). It allows administrators to set a specific IOPS threshold, distributing I/O requests once the threshold is met. This helps to balance the load more effectively based on the actual I/O workload.

      2. Path latency [Latency]

         • It actively monitors paths for latency and outstanding I/O, dynamically selecting the optimal path(s) to avoid higher latency or potential hardware issues. This results in improved load balancing and performance.

Environment

VMware vSphere ESXi 6.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Resolution

To check the vCenter UI:

• On vCenter UI, You can set Path Selection Policy as "Round Robin (VMware)", however the "Policy type" is not visible.
  
  
  • Select the ESXi on which you want to check
  • Configure > Storage Devices>
  • Select the Storage device > Properties >
  • Under Multipathing Policies - you can see the Path Selection Policy

Example Screenshot:

Execute the following command on the ESXi command line to determine if the Path Selection Policy type is set to Latency or IOPS:

 

To check from ESXi Command line:

• Command to see all the Storage NMP devices connected to this ESXi  host.:

esxcli storage nmp device list

 

• Command to see Storage NMP for exclusive device:

esxcli storage nmp device list -d <device NAAid>

 

Similar output is noticed:

 

 

"{policy=latency}",  This indicates the policy type is set to latency,.  the default "latencyEvalTime" value is set to 180000 millisecond [3 minutes]

 

"{policy=iops}",       This indicates the policy is set to IOPS, the default "iops, value is set to 1000.

 

 

Note: This setting is set on a per-host and per-device basis.

 

To change the  Path Selection Policy "type":

 

Command to change the Path Selection Policy "type" from Latency to IOPS :

esxcli storage nmp psp roundrobin deviceconfig set --type=iops --device=<device NAAid>




Additional Information

VMware Multipathing policies in ESXi/ESX

VMware Path Selection Plug-Ins and Policies

Viewing and Managing Storage Paths on ESXi Hosts