Survivor Bias

Apropos second generations, our second generation ATCA lineup was announced and it has 10G all over. This Eweek article
was printed back in November, but may still be news to readers of my sparse blog.

10G and ATCA are a great fit because no optics are needed to run 10G between blades and fabric. The server 10G cost barrier is gone. Gone is another 10G adoption barrier, the need to upgrade both the server and the switch at the same time. Our ATCA refresh is quite comprehensive, with UltraSPARC T2 and x86 processors, with 10G in the blades (Neptune), in the fabric, through RTMs, and with server and packet processing on the same blade (see previous blog entry).

As all-things-ATCA get interesting some observers ask about the one or two competitors that quit. As a Telco and Carrier platform supplier we definitely like the technical, market, and standard attributes of ATCA. Though some may argue that our perspective carries "Survivor Bias".

The Survivor Bias artifact, in finance and in statistics, is the hazard of excluding population samples that did not survive. Like measuring the growth of all public companies yet overlook the companies that went under. Or worse, the ones that went under and survived (ask me how I know).

Recently I tasted Survivor Bias when our instructor wrapped up a leadership training course. The closing, the Grand Finale, was an attempt to put our professional travails in perspective by hearing what famous people thought really mattered in life, in retrospective, mind you. I silently cried foul. I felt that the success of these quotable luminaries tainted their collective wisdom with Survivor Bias. Their perspective devalued the priorities that consume most of my daily energies. And sure enough they no longer worry about the daily grind. Their job is done.





It took me a while to recognize two distinct objections at play, one has to do with judgment calls a posteriori, once the outcome is known, and the other with the effect of survival itself on the validity of the data.

The temporal objection is against the natural diminution of bridges already crossed. If our preoccupation is to be a strong link in a much longer chain, once the chain goes on, our opinions and priorities are of much lesser value. My objection against judging past priorities stands.

Outside of hindsight the value of the survivor perspective may depend on the survival process. The Car Talk radio show had a puzzler where a mathematician recommends armor plating WWII airplane wings and fuselage in spots where the returning airplanes showed no bullet holes. Absence of holes does not mean the area is not exposed, but possible vulnerability, if there is a correlation between planes hit in those spots and planes not returning.

This is just to illustrate how survivor data validity depends on whether we think survival stochastics are random or correlated. The example is neat because given a large sample, the mathematician can determine both the existence of the correlation, and the areas to protect.

Back to ATCA, our perspective is timely rather than "a posteriori", so we are safe there. And Sun's Netra platform success in the Telco market was not random, so on the correlation front we are peachy. Finally, we vote our perspective with a new generation of ATCA products. Every generation reinforces wings and fuselage looking at its bullet holes. And at the bullet holes of competitors that did not return from the sortie.

Today's Links:

Sun Netra ATCA Blade Server

UltraSPARC T2 on ATCA

Opteron on ATCA

High Throughput Packet Processing White Paper



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