Checklist for ASP.NET / Database performance

Question

Recently our customers started to complain about poor performance on one of our servers. This contains multiple large CMS implementations and alot small websites using Sitef

Answer 1

Can't speak for Sitefinity, but will come with some tips for Sitecore.

• Use Sitecores caching whenever possible, esp. on XSLTs (as they tend to be simpler than layouts & sublayouts and therefore Sitecore caching doesn't break them, as Sitecore caching does to asp.net postbacks), this ofc will only help if rederings & sublayouts etc are accessed a lot. use /sitecore/admin/stats.aspx?site=website to check stuff that isn't cached
• Use Sitecores profiler, open up an item in the profiler and see which sublayouts etc are taking time
• Only use XSLTs for the simplest content, if it get anymore complicated than and I'd go for sublayouts (asp.net controls), this is a bit biased as I'm not fond of XSLT, but experience indicates that .ascx's are faster
• Use IIS' content expiration on the static files (prob all of /sitecore and if you have some images, javascript & CSS files) this is for IIS 6: msdn link
• Check database access times with Sitecore Databasetest.aspx (the one for Sitecore 6 is a lot better than the simple one that works on Sitecore 5 & 6) Sitecore SDN link

And that's what I can think of from the top of my head.