Re: HTTP Compression & Squid

> As you can see from http://www.mozilla.org/projects/apache/gzip/, adding
> compression significantly speeds up client access by up to 30% on a 28.8
> modem.
>
> The biggest problem I see is that gzip eats CPU, so obviously gzip -9 won't
> be the prefered compression method on large servers :)

The cache is really the wrong place to use gzip. gzip is optimised
for high compression at the expense of compression time (bzip2 even
more so); therefore it is best used in compress once, uncompress many
environments, i.e. compress on the source server, before storing, and
conditionally uncompress in transit. (Uncompressing is deterministic
and linear on uncompressed size.)

LZ77, I believe, predates LZW (compress) and I suspect LZW was
invented for this sort of on the fly compression even though LZ77 is
better.

On the other hand, you can get the same sort of benefit by
compressing the PPP link (above the modem) and for patent reasons,
some people use deflate for this, even given the CPU penalty. It is
argued that the compression gives a net saving as there are less
character interrupts.

-- 
David Woolley - Office: David Woolley <djw@bts.co.uk>
BTS             Home: <david@djwhome.demon.co.uk>
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