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Ard van Breemen ard at telegraafnet.nl
Mon Oct 22 10:16:00 CDT 2001


On Mon, Oct 22, 2001 at 10:46:47AM -0500, Michael E Brown wrote:
> On Mon, 22 Oct 2001, Hubbard, David wrote:
> > squid won't help you, it is a proxy that caches data
> > so if I were running squid on my end and accessed your
> > site all day, my squid proxy would cache your data for
> > me so I'd get quicker responses.
> Sorry, but squid _can_ help, in a big way, depending on your content. 
> http://www.google.com/search?q=squid+reverse+proxy
Yes.
I have done some testing on a va-linux 1220, comparable to a dell 1550:
With apache I can get about 3300 requests/second for zero sized html
pages with 40 requests parallel.
With a single squid in front of it this is about 1600.
With two squids in front of it, it totals between 2500 and 3000.
(Zero sized html is a perfect example of adservers that send redirects
to images, not images).

It seems that apache is faster. This is *correct*. But only for a few
connections parallel!

In practice however, users tend to have loooooong coonections...
Apache+linux still cannot handle big arrays of connections very well.
Squid can, for 1000 connections it is as fast as 100. It is handling
it's connections in a kind of batch mode: accept any new connections.
Read from all connections. Write to all connections. Close connections.
In practice it is the difference between a happy server and a dying
server. I guess squid starts to be interesting once you hit 1000
request/min.

Squid is a perfect example of why multi threaded programs (apache)
are nicer to program, but single threaded programs tend to be faster
for big numbers.

That's also the most important thing about your server: the Continues
Peak Performance. Thus: what is the average number of requests/s it can
handle during an hour.
And that's also the most important thing about your website: the biggest
peak of requests/s it gets during a minute, or less.
All other numbers are really not interesting.

PS: squid is a single threaded program. On smp systems, you need to run
multiple squids.
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