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Showing posts from September, 2008

Essential Complexity versus Accidental Complexity

This axiom by Neal Ford[1] on the 97 Things wiki:It’s the duty of the architect to solve the problems inherent in essential complexity without introducing accidental complexity.should be etched on to the monitor of every designer/architect. The reference is to software architecture, but the axiom really applies to designing and building systems in general. The concept expressed in the axiom is really a special case of ‘build the simplest system that solves the problem', and is related to the hypothesis I proposed in Availability, Complexity and the Person Factor[2]:When person-resources are constrained, highest availability is achieved when the system is designed with the minimum complexity necessary to meet availability requirements.Over the years I’ve seen systems that badly violate the essential complexity rule. They’ve tended to be systems that were evolved over time without ever really being designed, or systems where non-technical business units hired consultants, contractor…

Unplug Your Wall Warts and Save the Planet?

Do wall warts matter?

(09/29-2008 - Updated to correct minor grammatical errors. )

Let's try something unique. I’ll use actual data to see if we can save the planet by unplugging wall transformers.

Step one – Measure wall wart power utilization.
Remember that Volts x Amps = Watts, and Watts are what we care about. Your power company charges you for kilowatt-hours. (One thousand watts for one hour is a kWh).

Start with one clamp-on AC ammeter, one line splitter with a 10x loop (the meter measures 10x actual current)and one wall wart (a standard Nokia charger for an N800).

And we have zero amps on the meter.

OK - That meter is made for measuring big things, so maybe I need a different meter. Lesson one Wall warts don't draw much current. They don't show up on the ammeters' scale even when amplified by a factor of 10.

Try again - this time with an in-line multimeter with a 300mA range.

Children - don't try this at home - unless you are holding on to your kid brother and…

The Path of Least Resistance Isn't

09/29-2008 - Updated to correct minor grammatical errors.

When taking a long term view of system management

The path of least resistance is rarely the path that results in the least amount of work.
As system managers, we are often faced with having to trade off short term tangible results against long term security, efficiency and stability. Unfortunately when we take the path of least resistance and minimize near term work effort, we often are left with systems that will require future work effort to avoid or recover from performance, security and stability problems. In general, when we short cut the short term, we are creating future work effort that ends up costing more time and money than we gained with the short term savings.

Examples of this are:
Opening up broad firewall rules rather than taking the time to get the correct, minimal firewall openings, thereby increasing the probability of future resource intensive security incidents.Running the install wizard and calling it pr…