Example: Usage Definition

March 16, 2008

Having defined the key system functions and the user population it is now necessary to define how the users place a functional demand on the system. (The online version of this article has more detail again.) The first part of this definition is to lay out how the usage of the system varies over time. Thus the relative usage of the system needs to be defined. The initial definitions are on an intra-hour, hourly, daily, weekly and monthly basis. These figures effectively have no units and simply provide a relative level of usage. Thus any metrics that are available to allow calibration of this data can be used. As an example, estimated percentage utilisation of the system for the time period could be provided. Alternatively, there may be historical data available from a production system. Read the rest of this entry »


From the news: Computing power for hire

March 15, 2008

I find it interesting that both Google and Yahoo are getting involved in super computers – and hiring or loaning out the results to others. The following article makes the point:

Yahoo! outsources! India’s! giant! supercomputer!

This is a HP/Yahoo initiative that seems to be a match for a recent IBM/Google move. Read the rest of this entry »


How should IT strategy work?

March 15, 2008

It is interesting that in many IT organisations “Strategy” has a bad reputation. In one organisation that I worked with there was a comment made that anything that was strategic would be removed the next year, whereas a tactical solution would still be there in thirty years. Read the rest of this entry »


Example: Defining users and locations

February 16, 2008

Specification of the user structure within the model

Location definition

For the purpose of this example the primary locations to be modelled will be the UK, New York, Europe and the primary and secondary data centres. These locations have been chosen to illustrate the use of different usage patterns across time zones, as well as to allow the effect of adding disaster recovery planning to be considered. For later use each of the locations also has a network node defined. In this case the nodes have simply been numbered sequentially for each of the locations. This will be discussed in more detail later. Read the rest of this entry »

Do your users think?

February 15, 2008

When designing a set of performance tests it is necessary to consider pauses between user interactions. This is usually referred to as “think time”, and represents the time between the system presenting the results of an action and the next action being taken. If a load test script doesn’t include any think time at all then the system will be bombarded with requests at a rate that isn’t humanly possible. Depending on the system there are likely to be between 10 and 100 times the interactions generated with zero think time than with realistic scenarios. Read the rest of this entry »


Performance and cost of ownership

January 15, 2008

What is the relationship between the performance of a system and its cost of ownership? This isn’t the start of a bad joke, but a question that I have needed to consider in detail recently. The question is more involved than it may seem initially, because of the factors that are implicit in the necessary analysis: Read the rest of this entry »


Is innovation good for performance?

November 15, 2007

A question I have been considering recently is whether innovation is good for performance. If I was writing about business performance the answer would hopefully be yes – but I am considering IT systems performance. Read the rest of this entry »


You can’t manage performance until…

October 15, 2007

A difficult challenge that comes up regularly is the idea that performance assurance starts with Volume and Performance testing. The assertion is that unless detailed performance data for the solution is available then there is little that can usefully be done. I have touched on an alternative approach in my “Principles of Capacity Management” document, where I examine what can usefully be done at different project stages. Read the rest of this entry »


Stakeholders in performance management

September 15, 2007

I have observed that few organisations really buy in to performance management until they have a performance problem. When an organisation has a performance problem they want to fix it. Now. A lot of work then goes into fixing the problem and then the team is disbanded or looses focus until the next performance problem arises. This reactive approach is not universal, but it is common. The approach is often augmented by a volume and performance test stage as part of the final testing, which is then inevitably squeezed out. Read the rest of this entry »


Customer relationships and sales pressure

August 15, 2007

I was recently in a meeting where a project was being initiated that needed a test facility for integration of different packages. I won’t go into the detail since it isn’t relevant to the overall discussion, and performance wasn’t the primary issue. I was struck by the usual “we can’t be the first people to need this” feeling and so, to cut a long story short, ended up calling Compuware to find out what they could offer. Read the rest of this entry »