My site has randomly slow performance when loading images. I have selected to cache my images on the file system and in the database. I am also using CMSFullClientCache = true as well as have applied a fix for the Expires header to be set.

When I inspect my page request I noticed all images are returning 304 Not Modified with a Expires header value 4 hours in the future (as per the cache setting). However, on some of these images Firebug is showing it the browser is waiting between 500 and about 2000ms per image. This is usually the first few images on the page but not always the same images. I get this on my dev environment, my QA environment and in the production environment.

Automated monitoring / alarming is occasionally reporting timeouts on requests to getattachment, where the call is taking more than 50 seconds to return. This is happening for a number of issues and the duration of this problem is something I can't manually reproduce.

I can however reproduce, on every request, the instance where some images take between 0.5 and 2 seconds to return, even through the browser has recieved a 304 Not Modified. I'm wondering if this is related to the problem on production.

Low level hardware alarming is not reporting excessive disk , cpu , or memory usage at any time. Usually running at around 5%-10%. The qa and production environments use a load balanced web farm of two web servers and the database in each environment is in active/passive mode (1 load balancer, 2 web servers, 2 db servers in each of qa and production).

Some further advice in resolving this matter would be most appreciated, as my customer has been really pushing this issue and I'm all out of ideas.

Thanks.