For many software architects, hardware capacity planning is a topic that lies beyond their comfort zone, yet it remains an important part of the architect‘s job. There are a number of reasons software architects often fail to properly consider hardware but they mostly have to do with a lack of understanding and unclear requirements.
The primary reason we neglect hardware considerations is that we are focused on software and tend to ignore hardware demands. In addition, we are naturally isolated from hardware by high-level languages and software frameworks.
Unclear requirements are also a factor as they may change or may be poorly understood. As the architecture evolves hardware considerations will also change. In addition, our clients may not understand or be able to predict the size of their own user base or system usage dynamics. Finally, hardware is constantly evolving. What we knew about hardware in the past does not apply today.
Without hardware expertise predicting hardware configurations for systems to be developed is highly error prone. To compensate some software architects use large safety factors. Such safety factors are generally not based on objective assessments or founded in any methodology. In most of the cases, this leads to excessive infrastructure capacities that will not be utilized even in periods of peak demand. As a result, clients’ money is wasted on more hardware than a system will ever need.
The best defense against poor hardware planning is to work closely with an infrastructure architect. Infrastructure architects, unlike software architects, are specialists in hardware capacity planning and they should be a part of your team. However, not every software architect has the luxury of working with an infrastructure architect. In such cases there are some things a software architect can do to mitigate errors when planning for hardware.
Drawing on your own past experience can help. You’ve implemented systems in the past and so you have some knowledge of hardware capacity planning – even if it was an after thought at the time. You can also discuss the topic with your client and convince them to set aside funds for hardware capacity planning. Budgeting for capacity planning can be much more cost effective than buying more hardware than you need. In this case, horizontal scalability is the key – adding hardware as needed rather than over-buying in the beginning. To make a horizontal strategy work software architects need to constantly measure capacity and isolate software components to execute in performance predictable environments.
Hardware capacity planning is as important as software architecture and it needs to be given a first order priority whether you have an infrastructure architect on hand or not. Just like an architect is responsible to establish the links between business demands and a software solution, she is responsible to envision the links between hardware and software.