iSCSI SANs use Ethernet connections between hosts and high-performance storage subsystems.

On the host side, the iSCSI SAN components include iSCSI host bus adapters (HBAs) or Network Interface Cards (NICs). The iSCSI network also includes switches and routers that transport the storage traffic, cables, storage processors (SPs), and storage disk systems.

The graphic depicts two types of iSCSI connections, one with a software initiator, another with a hardware initiator.

The iSCSI SAN uses a client-server architecture.

The client, called iSCSI initiator, operates on your ESXi host. It initiates iSCSI sessions by issuing SCSI commands and transmitting them, encapsulated into the iSCSI protocol, to an iSCSI server. The server is known as an iSCSI target. Typically, the iSCSI target represents a physical storage system on the network.

The target can also be a virtual iSCSI SAN, for example, an iSCSI target emulator running in a virtual machine. The iSCSI target responds to the initiator's commands by transmitting required iSCSI data.