iSCSI technologies in HP ProLiant servers using advanced network adapters, 2nd edition

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Figure 3. Software stack for full offload iSCSI on the FlexFabric adapter.
Multifunction network adapters with accelerated iSCSI
Until recently, the typical server environment required separate connectivity products for networking,
storage, interconnects, and infrastructure management. HP multifunction network adapters function as
both iSCSI HBAs and Ethernet NICs, so they support multiple functions through a single connection.
Ethernet server adapters with accelerated iSCSI simplify network infrastructure by functioning as
network adapters and as storage HBAs, providing access to storage boxes and servers over a single
connection. HP multifunction adapters support hardware-assisted accelerated iSCSI operation― the
offloading of parts of the iSCSI software to the server adapter for improved system performance.
Accelerated iSCSI uses a TCP/IP Offload Engine (TOE) to execute parts of the iSCSI stack on the
adapter rather than on the server host OS. The TOE translates SCSI block commands into NIC packets
and manages their transmission and receipt. These functions include all of the following:
 Segments SCSI blocks into TCP/IP packets (including header replication) when sending SCSI blocks
to a target device
 De-segments packets back to iSCSI blocks when receiving data from a target device
 Manages acknowledgements and retransmissions
Accelerated iSCSI does not offload processing of iSCSI protocol. It is executed in the OS on the
server side. The multifunction network adapter still presents a PCI NIC function to the system, requiring
a virtual bus driver on the server to make the NIC look like a SCSI initiator to the operating system.