To determine if CHAP is enabled on an ESXi/ESX 4.x host:
Select the host.
Click the Configuration tab.
Click Storage Adapters.
Select the Software iSCSI Adapter.
Click Properties.
In the General tab, click on CHAP...
In the CHAP Credientals dialog, One-way CHAP (for all types of iSCSI initators) and Mutual CHAP (for software and dependent hardware iSCSI) can be configured.
For more information on the CHAP authentication methods, see the Configuring CHAP Parameters for iSCSI Adapters section of the iSCSI SAN Configuration Guide.
ESX3.x:
To determine if you have CHAP enabled on an ESX or ESXi 3.x host:
Select the ESX host you want to verify.
Click the Configuration tab
Click Storage Adapters.
Select the software iSCSI adapter. ESX 3.0 uses vmhba40 and ESX 3.5 uses vmhba32.
Click Properties.
In the window that appears, click CHAP authentication.
CHAP authentication is not being used
CHAP authentication is being used
If CHAP is enabled, click Configure to confirm that the password is as expected
Additional Information
Note: If CHAP authentication issues occur, be sure that the the IQN matches exactly on the host and the storage system. In some cases the storage array may convert uppercase characters to lowercase. If this occurs, you can uncheck the 'Use initiator name option' and manually correct the value in the 'Name' field so that it matches the storage array's configuration.
The CHAP name and secret are stored in/etc/vmkiscsi.conf.