[john2k]

Originally Posted by imported_silkroad

Actually that is only one "main goal" of a CDN.

I agree from an end-user standpoint but was commenting in regards to the business need that most CDNs appear to be working to solve. All of them seem to be focused on bringing the content as close to the end-user as possible in order to reduce network latency. Running fast non-overloaded equipment is pretty much a necessity for them, however there are times when CDN equipment does get overloaded.

They could easily solve the load problem by having a huge cluster of servers & equipment in a single datacenter, but that does not solve the network problem where latency can cause stuttering with streaming media, etc. This is why the CDNs have as many edge locations as possible, in order to address the network issues.

For example, you could host your images anywhere else regardless of quality and that would still reduce the load on your webserver. VPS, another dedicated server or even a clustered file hosting provider such as http://www.blueturbo.com/file-hosting.php Blue Turbo solves the server load issue, but not the network issue as they run a cluster from a single datacenter. The network issues generally are not nearly as significant for images as they are for video, though, which is why Blue Turbo makes sense for many (I considered using them, but I do not).

To see the real power and benefits of a CDN, we can use Highwinds for an example. They streamed coverage of the presidential inauguration to a peak of 625,000 concurrent visitors using 310Gbps bandwidth. They could have done this from a single datacenter, but the viewing would not have been optimal for some viewers due to the network issue.

In my opinion, that's what CDNs are really being created for. But, I use a CDN for basically the same reason as you. Last month I offloaded just under 50 million image views to a CDN. The sole reason that I began using a CDN wasn't about the network latency benefit but was to reduce load on my webserver until my new server is built & colocated. Even after my new server is online I might keep images running from a CDN but am not certain about that just yet.