Performance Metrics of WebBased Systems

The performance of web-based system will be measured in the following areas:

1 Load Size

The maximum number of users supported under normal and peak load conditions. Load size revolves around simultaneous and concurrent users. Simultaneous users have active connections to the same web site, whereas concurrent users are accessing the site at the exact same time. A workload profile, thus, consists of a likely user composition where the users perform various system operations. Simulating simultaneous users can be done by making sure the test scripts incorporate so-called think time. The purpose of think time is to ensure that not all user requests being simulated will occur at the same time. Removing think time from the test script makes sense if the goal is to stress test the web application by simulating concurrent users (Hagen, 2000).

2 Response Time

Response time, also referred to as latency, is the time elapsed until a request has been processed. Response times can be measured on both server and client, where the latter includes the request queue, network latency, as well as the time required by the server to complete request execution. Response time increase as the number of users increases, owing to higher levels of resource utilization on the system’s server and network. Response time can also be affected by factors not related to user load, such as database size and poor software implementation (Ricca, 2001). Web system end users typically perceive response time to be the amount of time taken from the moment they click the mouse to the moment that a new web page has been fully display on the screen.

3 Throughput

Throughput is defined as how much work the system can support. Throughput denotes the number of operations that can be completed in a given period of time, such as bits transmitted per second, bytes transmitted per second, HTTP operations per day, or million of instructions per second (MIPS). Byte transmitted per second is the most common measure of unit as far as throughput is concerned.

4 Resource Utilization

Utilization is simply the part of the capacity of a component that is actually being used. These components are CPU, RAM, Disk I/O and Network I/O. Resource utilization with respect to these components represents a cost in system operation. If resource utilization will be too high, then response time will be higher as well as a result of longer queuing delays. If resource utilization will be too low, then it could be assumed that a large amount of money has been invested for excess capacity (Lyer, 2005).

September 28, 2007 | Filed Under Testing/Quality Assurance 

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