If there are performance requirements for the product (ex: religion website) und
ID: 3582421 • Letter: I
Question
If there are performance requirements for the product (ex: religion website) under various circumstances, state them here and explain their rationale, to help the developers understand the intent and make suitable design choices. Specify the timing relationships for real time systems. make such requirements as specific as possible. you may need to state performance requirements for inidvidual functional requirements or features. (with an example for a religion website, how can I applay this to crete a website).
Explanation / Answer
Performance Requirements
The only way in which systems will meet their performance targets is for them to be specified clearly and unambiguously. It is a simple fact that if performance is not a stated criterion of the system requirements then the system designers will generally not consider performance issues.
Identifying Performance Requirements
-Is new introduced functionality introducing significant architectural change?
-What is the transaction rate that the expected change is estimated to be enacted per hour?
-How business critical is the new change?
-Can this be performance tested in isolation or do we require the whole system built together to performance test?
In order to assess the performance of a system the following must be clearly specified:
• Response Time
Whatever is chosen must be measurable in the real system. Care must be taken to ensure that the performance measurement is unambiguous, concise and completely defined. Response time specification should include the following information:
-Measurement Points: The points at which you want the response time measured needs to be included. For example are you interested in response time at the data centre or from a branch network?
-What is included: Define what is included in the measurement. For example does the measure for a web page include the browser render time or just the delivery time to the browser?
-What is excluded: Ensure calls to 3rd parties beyond the control of the system developer are defined. This is particularly important when defining contractual response time requirements, as suppliers can only be responsible for areas they can influence.
-Statistic Type: The statistic type needs to be defined. For example 95% of all response time should be less than 8.5 second.
-Measurement Period: Define the period over which to measure the response time. This is particularly important where workload varies over the day.
-Platform: Should it not be possible to test on the real production hardware any allowance for testing on test hardware needs to be stated.
-Error Rate: Define the acceptable error rate allowed during the measurement of the response times. Some systems may produce errors under high workloads and therefore the acceptable error rate need to be defined.
• Workload
The workload is often described as the scenarios that the users are likely to execute.The performance of the system is dependent on how the load is delivered to the system. For example it is easier to achieve faster response times for a system that receive an regular arrival of work throughout the day compared to one that receive burst of traffic. Therefore it is important that the workload profile is defined
• Scalability
scalability is simply specified as the increase in the system’s workload that the system should be able to process. The scalability required is often driven by the lifespan and the maturity of the system. For example, a new (and hence immature) system could suffer an unexpected growth in popularity and suffer from a significant increase in workload as it becomes popular with new users. More mature systems which represent improvements on older systems are likely to have more accurately defined workloads and thus be less likely to suffer in this respect
• Platform
A platform is defined as the underlying hardware and software (operating system and software utilities) which will house the system.It is not always the case that the designer will be given a “green field” choice of what platform on which to house the system.In some cases the customer may dictate this choice or there may be internal reasons (product strategy perhaps) that will constrain the designer’s freedom. It may also be the case that the system will require various generic products to be used in which case the performance of these must also be specified.
Timing relationships for Real time systems
-I/O
Real-Time systems interact with their environment by input/output subsystem. Sensors and actuators are the examples of i/o elements in real-time systems. On the otherhand i/o an important part of real-time systems.
-Fault Tolerant Computing
Fault tolerance is important in safety-critical real-time systems because otherwise a single component failure can lead to a catastrophic systems failure.
-Quality of Service
With the growth of Internet several multimedia applications like multimedia are merging with real-time systems. Scheduling in these systems is done to provide good quality of service. Some of the real-time systems research is being extended to QoS scheduling to multimedia applications.
An Example-
At a minimum, a set of performance requirements should document the following:
If the user denies interest in response time and indicates that only the result is of interest, you can ask whether "ten times your current estimate of stand-alone execution time" would be acceptable. If the answer is "yes," you can proceed to discuss throughput. Otherwise, you can continue the discussion of response time with the user's full attention.