Using a CDN to store/serve user image uploads?

Question

I'm still new to the whole CDN ideaology, so this might be a stupid question but I'm sure someone can shed some light on this. I've got a basic php script that takes user image uploads, resizes them, creates a directory ($user_id), and stores the finished product in the directory (like www.mysite.com/uploads/$user_id/image1.jpg). Works like a charm.

I just got all the hosting stuff squared away and I'm using the Rackspace (Slicehost?) "Cloud Server" architecture. I also signed up for the Rackspace (Mosso?) "Cloud Files". So far so good.

So my question is: Should I be storing the images that users upload locally (on my apache server) or as objects via Cloud Files? It seems like a great idea to separate the static content from my web server so I can just use it to generate the dynamic content. But would it be a lot of overhead to create a CDN-enabled Container each time a user uploads an image?

Hopefully I'm not missing the boat on this one totally. I can't seem to find a whole lot of info about this, but I'm sure there is a good reason why I should either pursue or avoid this idea. Any suggestions are greatly appreciated!

Answer 1

I am not familiar with Rackspace's offering, but the general logic behind using a CDN for static content is to achieve two goals:

1. offload the bandwidth and processing to other servers, freeing up yours.
2. move the requests off to the client
3. Move the large static content closer to the client

When you send the generated HTML to the browser, it will "see" the images as www.yourdomain.com/my_image.jpg for example, and perform additional requests for each piece of static content, potentially starving your server of threads to service requests. If you move all this content onto a CDN, the browser would see something like cdn.yourdomain.com, and the browser will request the images from the CDN, thus allowing your server to service other requests instead. Additionally, most CDN's distribute your content to multiple locations and have geographic routing for requests to serve the content from the closest possible location, improving the perceived load time for clients.