Making the Grade Comments

Managed to score an A in YSlow‘s Performance tab. This takes into account the treating of Flickr, LinkedIn, W3C and thyncology.com as CDNs.

The first makes sense as I’ll be serving up images from there for some time at this point. The second is a temporary concession; I need to make a local copy of the link image eventually and stop retrieving images from there, and the third is more interesting.

Another topic discussed in High Performance Web Sites is the maximum # of parallel downloads per domain. By the HTTP 1.1 standard this is 2. Browsers can choose to ignore this but by default they obey like Andre. However, a way around the 2 simultaneous download limit (without resorting to a true CDN) is accomplished through mirroring. The browser believes the source files (in this case a few scripts and a .swf) to have come from another site, though the files are located in the same structure. Brilliant, and as cheap a solution as any that can potentially double my # of downloaded components at a time.

Grade attained, I can finally sleep. Well. Soon.


  1. Posted December 19, 2007 at 11:41 am | Permalink

    These are some really weird workarounds, I must say. I don’t quite understand how any of those sites, save perhaps Flickr, could be used as content delivery networks, but I’m intrigued. Also am curious about configuring domain mirroring.

  2. Posted December 19, 2007 at 1:09 pm | Permalink

    Flickr is the only proper one, save thyncology.com. The reason it can be construed as such is that it allows for add’l simult. downloads, which is the main point of using a CDN. (the other being load balancing, which I of course have no $$$ to afford)

    The others have been written off as CDNs temporarily, as mentioned in the original post. In reality I’ll simply copy the now-foreign images and use them locally, which avoids touching the other servers entirely.

    Mirroring would of course vary per host. Dreamhost uses a simple form field upon creating or on editing any domain hosted with them to point the domain to any other domain. The point of mirroring and how it varies from redirecting is that the URL does not change from the client’s point of view. Here’s their wiki page on the subject: http://wiki.dreamhost.com/Mirror_Domain

    I’m hoping I don’t actually receive a penalty on the mirroring, (as the wiki page makes it clear this is a possibility) as it’s not harming anyone and was only done for the performance boost.

    Wow. I notice some crazy grammatical issues with the post I’ve got to correct. Guess that’s what happens with a 6am post.

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