Configuring/editing hardware/dependent hardware initiators

ESXi can access an iSCSI storage by using one of the following iSCSI initiator types:

• Software iSCSI initiator: ESXi manages the entire iSCSI stack and uses one or more VMkernel adapters and a virtual network. With the software iSCSI adapter, you can use iSCSI technology without purchasing specialized hardware.
• Dependent hardware iSCSI initiator: iSCSI management and configuration are managed by VMware, but part of the network stack is implemented at the NIC level using some iSCSI offload capabilities. At ESXi level, those NICs are presented with two different components—a hardware iSCSI adapter and a corresponding standard networking NIC.
• Independent hardware iSCSI initiator or iSCSI HBA: This is the same as an FC HBA; all of the network stack is implemented in hardware inside the adapter. On the ESXi side, you just see one or more vmhba, like with all other block storage adapters. Network configuration must be performed at card level, using BIOS management, or specific tools (there are also plugins for vCenter to manage the configuration inside vSphere).

CNA cards could appear fully independent or dependent on hardware adapters, but usually using NPAR as a real HBA.

The main difference between one mode and another is how the network is configured: only the independent hardware iSCSI adapter does not require one or more VMkernel adapters on a proper virtual network. Also, the host CPU usage will decrease from the software iSCSI to the HBA iSCSI, but performance and throughput are quite the same for all types of initiators.

For more information, see the vSphere 6.5 Storage guide (https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.storage.doc/GUID-7A4E3767-CB54-4E88-9BA8-298876119465.html).