AEM/CQ5 : AEM_Basics of Performance Common issues and how to prevent them

Area	Symptom(s)	To increase capacity...	To reduce volume...
Client	High client CPU usage.	Install a client CPU with higher performance.	Simplify (HTML) layout.
	Low server CPU usage.	Upgrade to a faster browser.	Improve client-side cache.
	Some clients fast, some slow.
Server
Network	CPU usage low on both servers and clients.	Remove any network bottlenecks.	Improve/optimize the configuration of the client cache.
	Browsing locally on the server is (comparatively) fast.	Increase network bandwidth.	Reduce the "weight" of your web pages (e.g. less images, optimized HTML).
Web-server	CPU usage on the web-server is high.	Cluster your web-servers.	Reduce the hits per page (visit).
		Use a hardware load-balancer.
Application	Server CPU usage is high.	Cluster your CQ5 instances.	Search for, and eliminate, CPU and memory hogs (use code review, timing output, etc).
	High memory consumption.		Improve caching on all levels.
	Low response times.		Optimize templates and components (e.g. structure, logic).
Repository
Cache

Performance issues may stem from a number of causes that have nothing to do with your website,
including temporary slowdowns in connection speed, CPU load, and many more.
It may also impact either all your visitors, or only a subset of them.
All this information needs to be obtained, sorted and analyzed before you can either optimize the general performance or solve specific issues.

Before you experience a performance issue:
- collect as much information as possible to build up a good working knowledge of the system under normal circumstances
When you experience a performance issue:
- try to replicate it with one (or preferably more) standard web-browsers, on a different client that you know has good general performance and/or on the server itself (if possible)
- check whether anything (related to the system) has changed within an appropriate time-space, and if any of these changes could have impacted the performance
- ask questions such as:
  - does the issue only occur at specific times?
  - does the issue only occur on specific pages?
  - are other requests impacted?
- collect as much information as possible to compare with your knowledge of the system under normal circumstances:

AEM/CQ5