Intel 170 Servers, AS/400 RISC Server, 7xx Servers manual Webfacing Compression

WebSphere Application Server. On System i servers, the recommended WebSphere application configuration is to run Apache as the web server and WebSphere Application Server as the application server. Therefore, it is recommended that you configure HTTP compression support in Apache. However, in certain instances HTTP compression configuration may be necessary using the Webfacing/WebSphere Application Server support. This is discussed below.

The overall performance in both cases is essentially equivalent. Both provide significant improvement for end-user response times on slower Internet connections, but also require additional HTTP/WebSphere Application Server CPU resources. In measurements done with compression, the amount of CPU required by HTTP/WebSphere Application Server increased by approximately 25-30%. When compression is enabled, ensure that there is sufficient CPU to support it. Compression is particularly beneficial when end users are attached via a Wide Area Network (WAN) where the network connection speed is 256K or less. In these cases, the end user will realize significantly improved response times (see chart below). If the end users are attached via a 512K connection, evaluate whether the realized response time improvements offset the increased CPU requirements. Compression should not be used if end users are connected via a local intranet due to the increased CPU requirements and no measurable improvement in response time.

Webfacing - Compression

(Seconds)	7
	6
	5
	4
Time
	3
Response	2
	1
	0
	64K	128K	512K	Local

Network Data Rate

Without

Compression

With Compression

NOTE: The above results were achieved in a controlled environment and may not be repeatable in other environments. Improvements depend on many factors.

Enabling Compression in IBM HTTP Server (powered by Apache)

The HTTP compression support was added with the latest set of PTFs for IBM HTTP Server for i5/OS (5722-DG1). For V5R1, the PTFs are SI09287 and SI09223. For V5R2, the PTFs are SI09286 and SI09224.

There is a LoadModule directive that needs to be added to the HTTP config file in order to get compression based on this new support. It looks like this:

LoadModule deflate_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008	Chapter 6 - Web Server and WebSphere	114