pierrefar - 12:26 pm on Jun 22, 2011 (gmt 0)
That's a very interesting approach, but as the rel="canonical" HTTP header is web search only at the moment, it will not work as you imagine right now. The more technically correct approach is to parallelize the images loading on page load, not parallelize the images themselves. To rephrase, the Page Speed recommendation is not to duplicate images across lots of sub-domains but it is to put multiple (non-identical) images of an HTML page onto different hosts. This means that each image has only one URL to be used throughout the site, but the different images on the page are on URLs on different hostnames.
To take your example, this kind of set up:
is better than having a situation of
In reality of course, i1, i2, i3, etc can be set up as CNAME or A records in the DNS to the same server or content distribution network or multiple IP addresses configured as per the Site Speed recommendations (e.g. to send browser caching headers).
Hope this helps,