Avoid Contention For Resources
Unless you’ve specifically designed your load test to include them, the most accurate, consistent results will come from tests that do not compete for resources with other processes – particularly sporadic, uneven processes.
If the site’s peak traffic is at 2pm and the least traffic is at 2am, it may be tempting to run your load tests at 2a. Have you checked the backup schedule with the sysadmins? If your backups run at 2:30a, you could spend hours diagnosing strange performance anomalies that could not be reproduced in a second test at 4a. Sounds obvious, right? But it happens all the time – usually because the testers don’t even know it is happening. Find out!
Events to look for:
- database re-indexing jobs
- scheduled cache/pool flushes
- backups, including backups of unrelated systems that can hog bandwidth or SAN capacity
- anything else that is scheduled for automatic execution
Put them on your load-testing calendar so you will be aware if/when they will affect your tests.
Chris Merrill, Chief Engineer
When his dad brought home a Commodore PET computer, Chris was drawn into computers. 7 years later, after finishing his degree in Computer and Electrical Engineering at Purdue University, he found himself writing software for industrial control systems. His first foray into testing software resulted in an innovative control system for testing lubricants in automotive engines. The Internet grabbed his attention and he became one of the first Sun Certified Java Developers. His focus then locked on performance testing of websites. As Chief Engineer for Web Performance since 2001, Chris now spends his time turning real-world testing challenges into new features for the Load Tester product.