Using a subdomain for images - improve speed?
 

Ive heard of people using a subdomain for images on their site because the web server apparently sees the subdomain as a different domain and therefore more concurrent connections can be achieved (as they are normally limited to 2 or 3).

This is a new concept, so I appologise if im talking out of my arse with this one, but ive heard it mentioned a few times. Can anyone shed some light on this?

Regardless of dns pointing, if the pointing takes you back to the same server there is no advantage if that server is already over burdened.

If you want to proxy the images out, that you can do, i would suggest nginx to proxie thru, dump all image calls to a separate image server, the rest can stay local.

It can speed things up for the user if they are not using too much bandwidth at a given time, and can handle the extra concurrent downloads. Tons of sites do it - but they usually also have it on a different server to handle static requests quickly.

use a CDN such as Amazon S3 to serve all static files (ie. images, js, css)

the goal...

1. decrease server load
2. decrease bandwidth
3. decrease cost
4. decrease page display time

you can cname your domain to point to your amazon s3 server account (url)

-- Make sure that the domain you use is not the same as the domain you use for your site ... you don't want them to be the same because your cookies will be associated with each static file (some cookies can be as long as 1k which will increase your time)

for example, your site domain is domain.com ; you should purchase domain-file.info to serve your static files (as long as it's a different domain your ok)

you can then create the following sub-domains:

• js.domain-file.info to serve javascript files
• css.domain-file.info to serve stylesheets
• img.domain-file.info to serve all images
• icons.domain-file.info to serve icons if you have a large amount of icons

- You also want to make sure that you add EXPIRES header so that the static files are cached - saving you bandwidth and decreasing overall page display time

I use Bucket Explorer for uploading static files to my amazon s3 account.

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To further decrease page display time, I recommend compressing (gzip) your js and css files. You will then have to create a plugin to show gzip version if browser is capable of displaying if not show the uncompressed version. Most modern browsers are capable of displaying compressed files. However, IE6 is known to have some issues even the SP2 which was reported to have this fixed is still buggy.

http://www.browserscope.org/ will give you an idea of how a browser functions .. knowing this can help you speed up your pages


other things you can do to speed up your pages...

• get rid of tables or use them less frequently; have small tables not large
• remove javascript
• combine javascript (decrease http request)
• combine css (decrease http request)
• combine images using sprites (decrease http request)
• use less javascript - javascript blocks everything from loading (concurrently) until completely loaded ... this is why I highly recommend that css gets loaded prior to any javascript calls

Thank you very much for your replies, especially Princeton's. I very interested in getting improved performance out of my site and this is a huge help.

sumbitted the above as an article...
Improve Web Page Performance

Couldnt agree more, this is an area I have never ventured, and looks very interesting. Thanks

I didn't mention this before but using a CDN is also good if you run multiple forums with same images. eg. icons, smilies, custom images, etc

I had a separate subdomain another server for serving the images and files and I have load and processes dropped to half.