《Systems Performance: Enterprise and the Cloud》读书笔记系列（七） —— 第二章（六）

1. Ad Hoc Checklist Method: Step through a canned checklist is a common methodology used by support professionals when asked to check and tune a  system, often in a short time frame. These checklists are ad hoc and are built from recent experience and issues for that system type.

2. Problem Statement: Defining a problem statement is a routine for support staff when first responding to issues. It's done by asking the customer the following questions: 

1) What makes you think there is a performance problem?

2) Has this system ever performed well?

3) What changed recently? Software? Hardware? Load?

4) Can the problem be expressed in terms of latency or runtime?

5) Does the problem can affect other people or applications (or is it just you)?

6) What is the environment? What softwares and hardwares are used? Versions Configuration?

Just asking and answering these questions often points to an immediate cause and solution. The problem statement has  therefore been included here as its own methodology and should be the first approach you use when tackling a new issue.

3. Scientific Method: The scientific method studies the unknown by making hypotheses and testing them. It can be summarized  in the following steps: 

1) Question

2) Hypothesis

3) Predication

4) Test

5) Analysis

The question is the performance problem statement. From this you can hypothesize what the cause of poor performance may be. Then you construct a test, which may be observational or experimental, that tests a predication based on hypothesis. You finish with analysis of the data collected.

4. Diagnosis Cycle: hypothesis->instrumentation->data->hypothesis. The cycle emphasizes that the data can lead to quickly to a new hypothesis, which is tested and refined, and so on.