To gzip or not to gzip?

That is the question...

It can speed up page loads for members. But at what cost in terms of server load and resources?

The thing to consider, besides overhead, which is not really a part of the gzip debate, is whether the users client can deflate compressed data. The norm from that I see is that most implementations of the client side only deal well with compressed type text/html.

Now I'm no expert on this, but there are many documents at apache that can be referenced.

What is see is that mod_deflate is referenced in apache 2.0 and 2.2 this used an external extension of apache.
http://httpd.apache.org/docs/2.0/mod/mod_deflate.html
http://httpd.apache.org/docs/2.2/mod/mod_deflate.html
Reference "output compression" on 2.x and you'll notice directives need to be set judiciously. To be honest, I'm more confused then informed.

Mod_gzip appears to be used on 1.3 and this seems to be an external add on for apache. I see no internal docs on this at apache.

vB seems to rely on the php extention of zlib.

Looking at the vB files and because with shared servers we can't predict what version of apache will be run nor how apache is configured, zlib seems to be coded to be handled by php. http://us3.php.net/manual/en/ref.zlib.php

It appears to me that if php is not displaying a page, then there would have to be an apache extentsion to do the job. mod_gzip on apache 1.3 and mod_deflate on 2.x. Meaning when setting the zlib compression in vB, only vB output is affected via php zlib depending on what vB sees based on the client at the time init.php runs and the php.ini file's settings and run mode of php.

Other output on the server would seem to depend on the apache configuration and I'm not even sure if that would override any decisions vB forced php zlib to make and how.

There appears many circumstances where, even if enabled, the compression may not occur in vB. There are even circumstance where the zlib compression will be turned off depending on the type of data per page that vB is delievering. But again, I wonder how and apache configuration would affect that in the end?

Again, not being an expert, this is my understanding of it from reading vB files and apache docs. I didn't even stay in a holiday inn express last night. So milage may vary on my assessment of this.

an honest question here... one I feel silly in asking but it begs asking for all those who don't know....

What, exactly, is gzip?

*ducks*

an honest question here... one I feel silly in asking but it begs asking for all those who don't know....

What, exactly, is gzip?

*ducks*

I'm sure you have used winzip and the likes and understand that it takes a file and makes it smaller? Well, same thing. Except, in the context we are exploring here, it takes a web page before your server serves it and compresses it to make it smaller. This of coruse depends on the browser of the person visiting your site to be able to uncompress them or unzip them if you will. If the client sends the right headers, the compressed version of the page will be served and you can save resources. When it gets there, the browser unzips the page so it's readable.

This saves bandwidth and on a site with a lot of hits and or perhaps serving lots of large files, you can save loads of bandwidth.

But, as minstrel's post implies, there can be a perfomance hit. The more compression desired, the more work the CPU may have to do to serve the page. There are levels of compression. I believe that using one gets the desired result and does not cause a serious cpu hit.

However, that discussion is still on the table because I'm not an apache or zlib expert. I made some edumacated assessments.

Yes I use winzip on a regular basis.

So, in your opinion, which one is best? zip, or gzip? I only have experience with the one.

Yes I use winzip on a regular basis.

So, in your opinion, which one is best? zip, or gzip? I only have experience with the one.

That's a whole other thread in this case.

In short, zip is a free windows compression program and very popular. Gzip is part of some/many linux commands for compression. Both are probably available in each OS for that matter.

For all I know, both use the same algo. Both are for compression, the algo of compression sets them apart.

ahha, ok thanks for the information

We're not discussing file compression per se, Peggy. We're talking about a vBulletin option to compress (gzip) the pages it sends to your forum members.

It seems to me that, with bandwidth less and less an issue, and more and more people on high speed (other than me), the potential speed increase of using gzip may be offset by the performance hit on the server.

Supplementary question for noppid: Is there any way this might take a performance hit on MySQL in particular? It seems unlikely to me but I'm curious.

We're not discussing file compression per se, Peggy. We're talking about a vBulletin option to compress (gzip) the pages it sends to your forum members.

It seems to me that, with bandwidth less and less an issue, and more and more people on high speed (other than me), the potential speed increase of using gzip may be offset by the performance hit on the server.

Supplementary question for noppid: Is there any way this might take a performance hit on MySQL in particular? It seems unlikely to me but I'm curious.

I don't think mysql comes into play in any way at all regarding the zlib libs used. It's happening after the queries and on the formatted output that is going to be sent to the end user if I understand it correctly.


The zlib extension offers the option to transparently compress your pages on-the-fly, if the requesting browser supports this.


But someone out there may be using zlib in php to compress and decompress data being stored in a mysql database trading off the cpu usage to conserve disk space. However, I can't comment on whether or not there would be an advantage to that.

We're not discussing file compression per se, Peggy. We're talking about a vBulletin option to compress (gzip) the pages it sends to your forum members.


ahh that's what I was asking... what exactly is gzip. Now I understand better. Thanks

ahh that's what I was asking... what exactly is gzip. Now I understand better. Thanks

Gzip is a compression algorithm. There are other algorithms for compression.

I think one reason for the ubiquity of gzip is that it is open source, n'est-ce pas?

Yes, probably so. But until today, I never really gave it a thought.



Yes, I found a french dictionary