When setting Host I/O Limits on a Storage Group, what are the available dynamic I/O distribution modes?

When configuring Host I/O Limits (a Quality of Service feature) for a Storage Group on a Dell EMC PowerMax array, there are three specific modes to control how the I/O limit is distributed across the front-end directors. These modes are:

Never: The I/O limit is statically divided among the available front-end directors. The allocation does not change.

OnFailure: The limit is statically divided, but if a director fails, its share of the I/O limit is dynamically redistributed among the remaining active directors.

Always: The I/O limit is continuously and dynamically balanced across all active directors based on their real-time workload, ensuring optimal resource utilization.

B. "Balanced Always" is not an official mode name. The "Always" mode is the one that performs dynamic balancing.

C. "Balanced" is not a distinct, selectable mode. It describes the behavior of the "Always" mode, but is not an option itself.

D. "Balanced" is not a selectable mode. The three available modes have the specific names Never, OnFailure, and Always.

1. Dell EMC Solutions Enabler Symmetrix CLI 10.0.0 Command Reference Guide

Page 778. In the set storagegroup command syntax

the -dynamicdistribution parameter is described with its valid values: "Specify the dynamic distribution setting for Host I/O Limits. The valid values are: Never

OnFailure

Always."

2. Dell EMC Unisphere for PowerMax Online Help (Version 10.0)

Section: "Provision Storage > Storage Groups > Modify Storage Group > Performance > Host I/O Limits". The user interface presents a dropdown menu for "Dynamic Distribution" which explicitly lists the options "Never"

"OnFailure"

and "Always".