# Charlottesville Coffee Roasters

One of the things I appreciate about living in beautiful Charlottesville, Virginia is the abundance of artisanal products that are high-quality and produced locally. There’s a vibrant network of people making food, drink, and physical goods: wineries, chocolate, art, blacksmithing, and much more. Many of our local producers are recognized worldwide. As a newly minted coffee lover, I also appreciate the variety and quality of coffee roasters in town and nearby. Of course, we have to import the beans, but there’s much to the coffee story after the beans are harvested. Here are some of my favorite local coffee resources.

# Simple Guidelines For Maintainable Spreadsheets

The spreadsheet is one of the most powerful inventions in the history of computing. But with that power comes responsibility: just as with a programming language, the spreadsheet itself can become difficult to understand and maintain.

# The Best Activity Tracking Watch

After thinking about smart watches, activity trackers, and similar devices for a while, I bought a Withings Steel HR. My goal was to find a traditional stylish-looking watch with long battery life, heart rate tracking, sleep tracking, and activity tracking. Here’s my experience thus far.

# How Venture Capitalists Have Helped Me

Venture capital is a competitive industry. Investors compete to win the best companies, so they pitch founders on the value they bring to their portfolio companies. When I was a new founder, their pitches didn’t resonate with me. I found it difficult to understand how they could help. A few years later, I get it; they really can add value. This is what I’ve found so far.

Leadership is, by definition, a process of transition. None of us is born to be a leader. Those who are leaders have become leaders through change, and it is a very difficult and unnatural process. A lot of this process involves learning, through repeatedly asking and answering the question, “what does a leader do?”

As a first-time CEO, I ask this question of other CEOs again and again, and write down their answers. I also find food for thought in blogs and books. As you might expect, answers from different CEOs differ a lot, but they have similarities.

# Product Market Fit

The way I think about product/market fit has changed a lot over the years. I view it differently than I used to.

# The Erlang Response Time Stretch Factor For 3 And 4 Servers

In a previous post I explored a few variations of equations that express the M/M/m queueing theory response time “stretch factor,” and tried to indicate some areas where I wanted to dig into the relationships between these formulas a bit more. In this post I discuss the divergence between the official Erlang C formula and Neil Gunther’s heuristic approximation to it. I introduced this before thusly:

At $$m=3$$ and above, the heuristic is only approximate. What does the Erlang form reduce to for the first of those cases? Does it result in the missing term that will extend to 4 and beyond too?

# Better Than The Golden Rule

The so-called Golden Rule is well recognized within Western culture, although most other cultures have similar concepts. Can you do better? I think the answer is yes, and it’s good to try.

# The Queueing Knee, Part 2

Last week I wrote about the so-called “knee” in the M/M/m queueing theory response time curve. In that post I examined one definition of the knee; here is my analysis of the others, including the idea that there is no such thing as the knee.

There are potentially several ways to think about the “knee” in the queueing curve. In the previous post I dug into Cary Millsap’s definition: the knee is the point where a line tangent to the queueing curve passes through the origin:

Here are a few others to consider:

# The Queueing Knee, Part 1

The “knee” in the M/M/m queueing theory response time curve is a topic of some debate in the performance community. Some say “the knee is at 75% utilization; everyone knows that.” Others say “it depends.” Others say “there is no knee.”

Depending on the definition, there is a knee, but there are several definitions and you may choose the one you want. In this post I’ll use a definition proposed by Cary Millsap: the knee is where a line from the origin is tangent to the queueing response time curve. The result is a function of the number of service channels, and although we may argue about the topics in the preceding paragraph and whether this is the right definition, it still serves to illustrate important concepts.

# A Great Mid-Priced Stereo System

You probably know that I like to be pretty minimalistic, and don’t accumulate a lot of “stuff” in my life. Yet for the few material things I value, I try to find the sweet spot: quality above average, price no higher than needed.

Music is one of the things I care a lot about: I have bought thousands of CDs. But I also value when my music sounds as good as possible. I treated myself to an upgraded stereo system so I’d enjoy better audio quality. Here’s my current system.

# 6 Steps to Better Security and Privacy

I wrote previously about securing your digital life. Technology and digital threats are advancing so fast that we’re almost inevitably all going to be attacked in some way. Here are a few more steps I’ve taken recently.

# Remembering Alan And Harry

Harry Weller died suddenly this week. Harry was one of the greatest venture capital investors in history. He led NEA’s investment in my company, VividCortex. Harry was an advocate and mentor to me, but he was more: in both life and death, he reminded me of Alan Rimm-Kaufman, a boss and mentor who died a handful of years ago.

# Excel Hacks To Ignore Missing Data

I’ve done quite a bit of work with Excel over the last few years, and I’ve found a couple of recurring problems when there’s missing or error data in ranges. I’ve had to work around this enough times that I thought it was worth sharing the solutions I’ve used.

# Forestry, a Static Site CMS

Forestry is a content management system that runs in your browser. On the backend, it integrates with a static site generator such as Hugo, letting you edit your static website in your browser just like any other content management system. I am writing this blog post with it on my iPad, using voice dictation.

# The Response Time Stretch Factor

Computer systems, and for that matter all types of systems that receive requests and process them, have a response time that includes some time waiting in queue if the server is busy when a request arrives. The wait time increases sharply as the server gets busier. For simple M/M/m systems there is a simple equation that describes this exactly, but for more complicated systems this equation is only approximate. This has rattled around in my brain for a long time, and rather than keeping my notes private I’m sharing them here (although since I’m still trying to learn this stuff I may just be putting my ignorance on full display).

# The Square Root Staffing Law

The square root staffing law is a rule of thumb derived from M/M/m queueing theory, useful for getting an estimate of the capacity you might need to serve an increased amount of traffic.

The square root staffing law is designed to help with capacity planning in what’s called the QED regime, which tries to balance efficiency with quality of service. Capacity planning is a set of tradeoffs: for best quality of service, you must provision lots of spare capacity (headroom), but that’s wasteful. For best efficiency, you minimize idle capacity, but then quality of service becomes terrible.

# Life on Mobile: The Last Mile on iPad

I wrote previously about how I run much of my life on iPhone/iPad, and how I switched from Android to iPhone. Why do I still have a laptop, if I can do so much on mobile devices? What holds me back?