How is Azure shared memory usage quota calculated?

Question

Windows Azure shared websites offer 512MB per Hour memory usage. However they offer little to no explanation as to how that number is calculated.

Is this the sum of all memory an application used during an hour? Or is it a peak amount of memory used at some point during the hour?

Answer 1

Windows Azure Websites uses a forest model where all the websites run in their own limited capacity region also called as AppDomain which is an isolation boundary within a IIS host (w3wp) process. AppDomains are designed to isolate and provide security around managed code that is executing within their host. Based on Windows Azure Websites type the AppDomain capacity is decided and the website application is limited to within those limits.

So the value you see with your memory usage gauge is the memory used by specific websites in that particular hour at the given time when the check was made. These checks are made once every hour and the value you see is the value at that given time. If shared websites is using over memory quota when check was made, the site is suspended for one hour, until the next enforcement period.