Scalability, a performance testing parameter that investigates a system's ability to grow by increasing the workload per user, or the number of concurrent users, or the size of a database.
Response Time
Throughput
Hits per second, Request per seconds, Transaction per seconds
Performance measurement with number of users
Performance measurement under huge load
CPU usage, Memory usage while testing in progress
Network Usage - data sent and received
Web server - Request and response per second