Unable to enable or disable the DelayedAck setting for a hardware iSCSI adapter

Products

• VMware vSphere ESX 7.x
• VMware vSphere ESX 8.x

Issue/Introduction

• vSphere Client: The DelayedAck setting is unchecked and grayed out, preventing any modifications through the GUI.
  
  
• Command Line (esxcli): Attempts to modify the setting using esxcli command fails with the error: "Unsettable parameter key."
  
  [root@esx###### :~ ] esxcli iscsi adapter param set -A vmhbax -k DelayedAck -v false
  Unable to set parameters: Unsettable parameter key: DelayedAck

Environment

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

Cause

The inability to modify the setting is due to a limitation enforced by the hardware iSCSI adapter's firmware or driver. The adapter's capability setting, Delayed Ack Settable, is explicitly set to false which prevents from directly enabling or disabling the DelayedAck feature at the adapter level.

esxcli iscsi adapter  capabilities get -A vmhbax
vmhbax
ISnS Settable: false
SLP Settable: false
Static Discovery Settable: false
Sendtarget Discovery Settable: false
Authorization Method Settable: true
CHAP Authorization Supported: true
SRP Authorization Supported: false
KRB5 Authorization Supported: false
SPKM1 Authorization Supported: false
SPKM2 Authorization Supported: false
Mutual Authentication Supported: false
Target Level Authentication Supported: true
Target Level Mutual Authentication Supported: false
Adapter Header Digest Supported: true
Target Level Header Digest Supported: true
Adapter Data Digest Supported: true
Target Level Data Digest Supported: true
ARP Redirect Settable: false
MTU Settable: false
Delayed Ack Settable: false
IPv6 Supported: true
DNS Based Address Supported: false
Inheritance Supported: false
IPv4 Enable Settable: false
IP Configuration Method Settable: true
Subnet Mask Setttable: true
Default Gateway Settable: true
IPv6 Enable Settable: false
IPv6 Prefix Length Settable: false
IPv6 DHCP Configuration Method Settable: false
IPv6 Linklocal Auto Configuration Method Settable: true
IPv6 Router Advertisement Configuration Method Settable: true
IPv6 Default Gateway Settable: true
Primary DNS Settable: false
Secondary DNS Settable: false
Name And Alias Settable: true

Resolution

Engage hardware vendor to determine the proper procedure (driver parameter, firmware setting, etc.) for disabling or enabling Delayed Ack setting on your specific hardware.