Availability Guide for Application Design

What Is Application Availability?

Availability Guide for Application Design—525637-004

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Analyzing Outages and Developing a Strategy

Clearly, the amount of effort you can put into making your application always available

is considerable. In most cases, a step-by-step approach to availability is appropriate.

Typically, as shown in Figure 1-2, a relatively small amount of effort can yield the most

significant results early, when initially improving availability. Costs typically increase as

you approach total availability.

To keep your availability goals on track, you should form an availability development

plan around the following elements:

1. Establish your availability goals.

2. Collect event and outage data for your application.

3. Perform an analysis of the cost of addressing each event and outage or set of

events and outages, and compare that cost with the benefit.

4. Eliminate those events and outages with the most benefit at the least cost.

5. Start again at Step 1 and reevaluate your availability goals.

Establishing Your Goals

Your availability goals are a business decision. They depend on the services provided

by the application, and upon factors such as the business you are in, and on what your

competition has to offer. Your goals will, however, vary over time. As the world comes

to expect increasingly reliable services, your availability needs will increase. A typical

business climate is therefore conducive to a phased approach to availability.

Having established your availability goals, you must establish how you intend to

measure progress towards those goals. These measurements might include collection

of outage data and collection of response time data.

Figure 1-2. Availability and Costs

Availability (in minutes of downtime)

2000

1000 500

Development

Cost

250

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