JavaScript vs. Server-Side Includes

[John R. Little]

I have a question regarding server performance issues of 
Server-Side Includes (SSI). 

Recently Sam Khosh-khui posted a question about using 
JavaScript to automatically generate the last-modified date 
for inclusion in web pages.  Christopher Lock responded 
with a few tips and mentioned that he wanted to use 
JavaScript to replace the similar SSI technique.  Chris 
mentioned that the SSI technique "entails a nontrivial 
performance hit on the server."

I don't know how to measure that performance hit but wanted 
to ask if anybody can verify or deny Chris's statement.  
Not too long ago I was reading Chuck Musciano's article 
"How to use server-side includes" in _Sunworld Online_
<http://www.sun.com/sunworldonline/swol-11-1996/swol-11-webmaster.html>.  
Musicano states that "Processing [SSIs] can be a 
time-consuming affair for some servers" but that "for the 
vast majority of servers, include processing is not 
expensive".  

In this case, will the JavaScript really be more efficient 
in terms of passing processing demand off to the client? It 
would seem like the processing power necessary to identify 
the last modified date of any particular file on a web 
server will still rely on server processing power rather 
than client processing power.  The difference being that if 
I enable SSI for the entire web site, the httpd will search 
for Imbedded SSIs in each and every file served. Conversely 
the JavaScript will only require server power in cases 
where the script exists.  I realize that one might not use 
the JavaScript for every single file in the htdocs tree but 
then again, one might.  With an automatically generated 
"last modified date" technique, I imaging it will/would get 
a lot of use.

Anybody know?  Or does anyone have suggestions on how 
I would measure performance and processor demand based on 
SSI vs. JavaScript?


--John
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  John R. Little       Web Developer/Systems Librarian 
  Perkins Library * Duke University * Durham, NC       
  VOICE: (919) 660-5932    Email: john.little at duke.edu 
              http://www.duke.edu/~jrl/
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