Web Server page compression tips Webserver Tips by Donald Burleson

Bandwidth is very expensive on busy web sites and there are many things that your webmaster can do to reduce your bandwidth and also improve your web page deliver speed.  Web sites without caching or compression have have huge delays because of over-stressed disks (enqueues for frequently-referenced pages and images) and there are two main ways to fix this, web page/image caching and HTML compression.  For my notes on RAM caching of web pages, see my webserver RAM caching tips.

What tools do HTML Compression?

This web site has a great list of many HTML compression tools:

HTML Compact - Replaces straight HTML tokenized JavaScript and a small decompressor, for JavaScript-enabled browsers. From AntsSoft.
 

mod_deflate - Included in the Apache 2.0 distribution.
 

mod_gzip - If you really need fine-tuning and advanced statistics, use mod_gzip instead. Currently an open source SourceForge project.
 

mod_hs - The Commercial Version of mod_gzip created by HyperSpace, Communications, Inc. HyperSpace claims a 30 percent performance increase achieved by in-memory compression and elimination of disk I/O operations.
 

mod_deflate ru (in Russian) - If you need fine-tuning and the best possible performance, try mod_deflate from sysoev.ru. See also documentation and mod_deflate ru tarball.

gzip_cnc

Let's take a look at the two most common HTML compression software tools, both within Apache.

Using Apache for HTML compression

You can utilize idle CPU resources by installing HTTP compression to improve webserver HTML delivery speed, trading off unused CPU cycles for faster web response time.  The two most popular HTML compression tools include:

• mod_gzip - Available on Apache 1.3, mod gzip compresses all outgoing HTML and the browser uncompresses the HTML at rendering time.
   

• mod_deflate - A newer tool, mod_deflate is available on Apache 2.0.  Mod_deflate is also available for Apache 1.3 on this Russian web site.

The only problem with HTML compression is that it does take a extra CPU resources, so it is a direct tradeoff between CPU and bandwidth resources.

Using mod_gzip

Older web site (using Apache 1.3) can benefit from HTML page compression with the Apache mod_gzip module.  It says here that mod_gzip has a fantastic HTML compression routine that works great with Apache 1.3. The 30%-60% bandwidth reduction makes me wonder why every web host is not using it:

"Webmasters typically see a 150-160% increase in Web server performance, and a 70% - 80% reduction in HTML/XML/JavaScript bandwidth utilized, using this module. Overall the bandwidth savings are approximately 30 to 60%. (This factors in the transmission of graphics.)"

Using mod_deflate

Mod_Deflate is available with later Apache releases (Apache 2) and it will compress whichever type of code you want once it is delivered to the client, and can save up to 80% on some pages.

On shared web servers, mod_deflate can be installed to only work for specific domains, so your ISP should be able to provide HTML compression just for your web sites.

If you running Apache 1.3, there are still ways to employ mod_deflate and also get web caching on Apache 1.3.  This Russian web site notes such a product. 

"mod_deflate is described in a recently published book by Andy King, "Speed Up Your Site: Web Site Optimization" in " Chapter 18: Compressing the Web" written by Konstantin Balashov.

Both modules have been in use on several heavily loaded Russian sites for more than 2 years. There are some English links: www.fastmail.fm success story by Jeremy Howard and the installation example by Philip Mak. "

In matters relating to HTTP compression, see my notes on Real-time web server traffic monitors - Live statistics, Webserver Traffic Monitoring Tips.  I have also prepared notes on the best webserver hardware configuration, and webserver RAM caching tips.