Performance Testing Guidelines specific to SharePoint 2010

Performance testing for SharePoint Server 2010 - The technet article provides comprehensive guidelines on how to go about planning to executing performance testing on SharePoint 2010. It provides useful information, pointers and guidelines on different aspects of performance testing - creating test plan, creating test environment, creating tests and tools. It has tips on some of important aspects such as whether to use think time or not, whether to enable parse dependent requests or not, whether to track virtual users or RPS etc.

Monitoring and maintaining SharePoint Server 2010 - Though the article is about general monitoring, but you can also use it to monitor your servers while performance testing. It provides useful information on what performance counters you should monitor, and what should be reasonable values. However, be aware that list of counters provided here is not the complete list of counters that you would need to analyse SharePoint 2010 performance. For example, the article does not provide info about very important counters about different kinds of cache - output, blob, object cache.