User`s guide

Chapter VII. iSCSI PDU Offload Target
Chelsio T5/T4 Unified Wire For Linux Page 99
1. Introduction
This section describes how to install and configure iSCSI PDU Offload Target software for use
as a key element in your iSCSI SAN. The software runs on Linux-based systems that use
Chelsio or non-Chelsio based Ethernet adapters. However to guarantee highest performance,
Chelsio recommends using Chelsio adapters. Chelsio’s adapters include offerings that range
from stateless offload adapters (regular NIC) to the full line of TCP/IP Offload Engine (TOE)
adapters.
The software implements RFC 3720, the iSCSI standard of the IETF. The software has been
fully tested for compliance to that RFC and others and it has been exhaustively tested for
interoperability with the major iSCSI vendors.
The software implements most of the iSCSI protocol in software running in kernel mode on the
host with the remaining portion, which consists of the entire fast data path, in hardware when
used with Chelsio’s TOE adapters. When standard NIC Adapters are used the entire iSCSI
protocol is executed in software.
The performance of this iSCSI stack is outstanding and when used with Chelsio’s hardware it is
enhanced further. Because of the tight integration with Chelsio’s TOE adapters, this software
has a distinct performance advantage over the regular NIC. The entire solution, which includes
this software, Chelsio TOE hardware, an appropriate base computer system – including a high
end disk subsystem, has industry leading performance. This can be seen when the entire
solution is compared to others based on other technologies currently available on the market in
terms of throughput and IOPS.
1.1. Features
Chelsio’s iSCSI driver stack supports the iSCSI protocol in the Target mode. From henceforth
“iSCSI Software Entity” term refers to the iSCSI target.
The Chelsio iSCSI PDU Offload Target software provides the following high level features:
Expanded NIC Support
 Chelsio TCP Offload Engine (TOE) Support
 T5/T4 Based HBAs (T5/T4xx Series cards)
Chelsio Terminator ASIC Support
 Offloads iSCSI Fast Data Path with Direct Data Placement (DDP)
 Offloads iSCSI Header and Data Digest Calculations
 Offload Speeds at 1 Gb and 10 Gb
 Offloads TCP/IP for NAS simultaneously with iSCSI
Target Specific features