HP 9000 RP4440 User Manual

TCP Segmentation Offload (TSO) Performance On HP rp4440 Servers

Using PCI-X 2-Port Gigabit Ethernet Cards

August 2004

Table of Contents

Introduction .............................................................................................................. 3

rp4440 Performance with GigE and TSO ..................................................................... 5

Service Demand: Less = More ..................................................................................... 6

Throughput: Faster = Better ......................................................................................... 7

Performance Highlights .............................................................................................. 8

Suggested Use .......................................................................................................... 8

Achieving High Availability with 2-Port Cards ............................................................. 8

Technology Combinations to Use or to Be Aware Of ................................................... 9

Test Details ............................................................................................................. 10

Products Used in Testing ........................................................................................ 10

Test Configuration ................................................................................................. 11

For More Information ............................................................................................... 11

Taking the Next Step ............................................................................................... 11

Legal Notices .......................................................................................................... 12

Introduction

This article highlights performance improvements available when you use HP’s TCP Segmentation Offload (TSO) capabilities in conjunction with the new A7011A and A7012A 2-port Gigabit Ethernet cards (Figure 1) in a powerful server such as the HP rp4440.

TSO works especially well in networks sending large amounts of data, such as in: web serving applications, data backups, or file transfer applications including NFS. TSO reduces CPU load thereby improving overall system response. Greater than 50% reduction in CPU

utilization has been observed on some FTP workloads.

Figure 1 HP PCI-X 2-Port Gigabit Ethernet Card (A7012A shown)

1. Not all applications benefit from TSO. Only data-intensive applications that transmit large data buffers using TCP over IPv4 are improved. Other types of applications will not significantly benefit from TSO. Performance improvements vary depending upon the hardware and software used. For details on recommended configurations, please refer to the section in this paper called “Technology Combinations to Use or to Be Aware Of.”

Introduction

TCP Segmentation Offload (TSO), also known as “large send” enables a system’s protocol stack to offload portions of outbound TCP processing to a network interface card thereby reducing system CPU utilization and enhancing performance. Instead of processing many small maximum transmission unit (MTU)-sized frames during transmit, the system can send fewer larger virtual maximum transmission unit (VMTU)-sized frames. On a typical Ethernet card, the link MTU is 1500 bytes while a VMTU can be much bigger. Currently, the VMTU size is fixed at 32160 bytes.

HP’s TSO is supported on Gigabit Ethernet cards including embedded or “core” LAN cards that are served by the iether or igelan software drivers running on HP-UX 11i v 1.0 and 2.0 or the September 2004 OE release of HP-UX 11i v 2. See “Taking the Next Step” in this

document, for how to obtain a free copy.

TSO requires no software configuration: once all

the required components are installed, it’s enabled automatically. TSO is supported on virtual LANs (VLANs). It’s supported at all speed settings on the link and all MTU values including Jumbo frames. Both Ethernet and SNAP encapsulations are supported. TSO does not work over link aggregates (HP Auto Port Aggregation), and if APA is present, TSO is automatically disabled.

The Gigabit Ethernet cards tested with TSO for this paper are the PCI-X 2-port A7011A card (with fiber-based connectors) and the A7012A card (with copper-based connectors). The 2-port cards provide the following benefits:

• Higher port density for I/O slot–constrained systems.

• Higher levels of failover protection, because two cards have no single point of failure.

The same level of failover protection would require four single-port I/O cards that would consume twice the number of I/O slots.

The cards also fully support HP Serviceguard and PCI-X/PCI online addition and replacement (OLAR).

• PCI-X I/O cards that are fully backward compatible with PCI 2.2 I/O slots.

• Flexibility for implementing Virtual Partition (vPars) configurations.

• Increased server CPU efficiency and performance through TCP, UDP, and IP checksum

protocol off loading.

• Increased network flexibility through support for virtual LANs (VLANs).

• A choice of either a 1000 Base-SX version using multi-mode fiber supporting distances

of up to 550m or a 1000Base-T version using CAT5 or better UTP cable supporting distances of up to 100m.

HP rp4440 servers like the one used in this demonstration are highly dependable, adaptable, and efficient servers for your enterprise. The results in this paper show that the A7011A and A7012A cards installed in a server like the rp4440 and combined with features like TCP Segmentation Offload (TSO) can increase your server efficiency while lowering your total cost of ownership.

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