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From Stephen Pierzchala <step...@pierzchala.com>
Subject [users@httpd] Content Compression -- mod_gzip v. mod_deflate
Date Wed, 05 Mar 2003 06:47:57 GMT
Having done a search of the list lately, there seems to be a real bias 
away from mod_gzip toward mod_deflate. For reasons that I have just been 
informed of, there is no "approved" mod_gzip for Apache/2.0.x. Instead, 
mod_deflate is being touted as a "suitable" alternative for content 
compression.

Well, it's not. It's ok, but mod_gzip -- and this will get me into 
trouble with the Apache Core team -- has a far better content 
compression algorithm than mod_deflate.

Best examples I can give are from my own servers. One is Apache/1.3.27 
with mod_gzip and the current production one is Apache/2.0.44 with 
mod_deflate

***

http://www.pierzchala.com/compress/homepage2.html
No Compression        56380 bytes

http://www.pierzchala.com/compress/homepage2.html
mod_deflate        19818 bytes
	-- DeflateMemLevel 8

http://www.pierzchala.com:9280/compress/homepage2.html
mod_gzip           16333 bytes
	-- Default configuration
	-- No source hack to increase gzip compression level applied

***

As well, mod_deflate appears to have a bug when you modify the 
DeflateMemLevel setting. A "9" is supposed to give maximum compression. 
Unfortunately, this is not the case.

***

Example #1
----------
http://www.pierzchala.com/resume.html -- 10924 bytes

Deflate Level        Byte Size
----------------------------------
     1        5520
     2        4993
     3        4719
     4        4589
     5        4521
     6        4500
     7        4488
     8        4473
     9        4483


Example #2
----------
http://www.pierzchala.com/compress/homepage2.html -- 56380 bytes

Deflate Level        Byte Size
----------------------------------
     1        25411
     2        22503
     3        21649
     4        20568
     5        20129
     6        20009
     7        19914
     8        19818
     9        19898

***

Could a setting of "9" adds so much more header information that it 
actually increases the file size?

I am throwing this out there to perhaps stir some open and frank 
discussion about the merits of the GZIP approach of mod_gzip versus the 
ZLIB approach of mod_deflate. I would like this to be discussed in the 
open, as the benefits of an improved compression module that is a part 
of the core Apache far outweighs the differences that separate the ZLIB 
from the GZIP camp.

smp

-- 

****

Stephen Pierzchala
stephen@pierzchala.com
http://www.pierzchala.com/


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