Tcp/Ip Offload Engine (Toe); Hardware Initiator - IBM TotalStorage DS300 Best Practices Manual

2.6.2 TCP/IP offload engine (TOE)

When using a TCP/IP offload engine, an iSCSI software initiator is still required,
but the TCP/IP processing along with the network driver are handled on a special
NIC. TOE is a hardware-based solution that removes the burden of IP processing
from the CPU on a server and moves it down onto the NIC. Data is written
directly to the NIC and it handles the IP processing necessary to transmit and
receive on the network. This implementation is faster than the previously
mentioned iSCSI software implementation since the host CPU does not have to
process the iSCSI IP packets. It has the added benefit that the TOE functionality
may potentially be used for all network traffic, not merely the iSCSI portions of it.
Note: A TOE may not allow you to run your standard TCP/IP connections off
the NIC unless the vendor has provided some type of filter driver to intercept
the standard TCP/IP requests.

2.6.3 Hardware initiator

The iSCSI initiator or driver can be implemented in a hardware adapter card,
rather than in the host software. This can be done by using an iSCSI host bus
adapter (HBA). The iSCSI processing is offloaded to the hardware adapter card
instead of processing the iSCSI protocol in the host software. iSCSI TCP/IP
processing is also offloaded to the TOE on the HBA. With both TCP and iSCSI
processing on the adapter card, high-speed transport of block data with minimal
CPU overhead is possible. This is the most expensive of the three iSCSI initiator
options as it require the purchase of an iSCSI HBA, but it is the most capable and
the best performer. All of the SCSI block-processing and TOE functions are
integrated into the HBA. This frees the host CPU from having to do any of the
iSCSI processing.
26
IBM TotalStorage DS300 and DS400 Best Practices Guide