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When is the use of a CDN wise?
02-03-2011, 11:03 AM (This post was last modified: 02-03-2011 11:16 AM by jesper_mortensen.)
Post: #4
RE: When is the use of a CDN wise?
@Geebee : What you could (or perhaps really should) do is to look at your analytics, and figure out which percentage of your users have really old browsers (IE6 era) and modern browsers (FF 3.5+ / Chrome 4+ , upcoming IE9, etc).

If you have many old browsers, then "sharding" your static assets over 2 or more hostnames (3rd level DNS names) gives a performance boost, due to the browser opening up multiple parallel downloads. (i.e. http://www.company.com with www-1.company-static.com and www-2.company-static.com as CNAMEs pointing to http://www.company.com.)

It's easiest to just use a single extra hostname, fx http://www.company-static.com.

If you use more than one extra hostname, you must take care to keep the "object" to "shard" mapping consistent. If "logo.png" is referenced as http://www-1.company-static.com/logo.png then it must stay that way. If it is later referenced on the other shard hostname www-2, then it will be re-downloaded.

Original source for this recommendation:
http://www.yuiblog.com/blog/2007/04/11/p...ch-part-4/

If your users have modern browsers, which will do 6+ parallel downloads from the same hostname, then you probably shouldn't do this. The extra time taken for the extra DNS lookups could eat up or be worse than the benefit.

For an overview of which browsers support many downloads from the same hostname, see browserscope.org.

HTH,
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When is the use of a CDN wise? - Geebee - 01-31-2011, 05:50 AM
RE: When is the use of a CDN wise? - jesper_mortensen - 02-03-2011 11:03 AM

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