Latency and the Speed of Light
Comments (3) Visits (10879)
Well, today is April 1, and I just love [April Fools' Day].This day has a rich history of practical jokes. Those not familiar can review this list of [Top 100 pranks and hoaxes].
Tim Ferris started the festivities with [The Grand Illusion: The Real Tim Ferriss speaks]. He claimed that for the past year, he outsourced the writing of his blog to a writer from India, and an editor from the Philippines. Given that his post was dated March 31, and he writes frequently about the benefits of outsourcing, it appeared like a legitimate post. However, Tim fessed up the following day, claiming that it was April 1 in Japan where he wrote it.
Guy Kawasaki wrote[April Fools' Stories You Shouldn't Believe]including my favorite #12 "Ruby on Rails cited Twitter as the centerpiece of its new 'Rails Can Scale' marketing program." Speaking of Twitter, Fellow IBM blogger Alan Lepofsky from our Lotus Notes team wrote[Great, now there is Twitter Spam]. It looked like a real post, but then I realized, ... everything on Twitter is spam!
Topics like energy consumption and global warming were fodder for posts and pranks.The post[Was Earth Hour a joke again?], argued thatthe preparation of "Earth Hour" last week in effect used up more energy than the hour of this annual "lights-off event" actually saved. This reminded me of John Tierney's piece in the New York Times ["How virtuous is Ed Begley, Jr.?"] where a scientist explains that it is more "green" for the environment to drive a car short distances than to walk:
If you walk 1.5 miles, Mr. Goodall calculates, and replace those calories by drinking about a cup of milk, the greenhouse emissions connected with that milk (like methane from the dairy farm and carbon dioxide from the delivery truck) are just about equal to the emissions from a typical car making the same trip. And if there were two of you making the trip, then the car would definitely be the more planet-friendly way to go.
Wayan Vota, my buddy over at OLPCnews, writes in his post[Windows XO Child Centric Development] that the "Sugar" operating environment on the innovative Linux-based XO laptops will soon be re-named the"Windows XO Operating System", with their new motto "Windows XO: A Child-Centric Operating Platform for Learning, Expression and Exploration." The mocked up photo of an XO laptop with the Windows XO logo was excellent!
Gretchen Rubin reminds us that this is a great day to play tricks on your kids in[How April Fool’s day can be a source of happiness], and last week, Kai Ryssdal on NPR Radio investigated if [Mind Habits] was [a video game that's good for you?]This claims that just playing five minutes per day can reduce stress. I haven't been able to stop playing after five minutes, Mind Habits is like the proverbial potato chip, you can't just eat one!
The economists from Freakonomics explain in [And While You're at it, Toss the Nickel] that it costs the US Government 1.7 cents to produce each penny. The US government loses $50 million dollars each year making pennies. Each nickel costs 10 cents to produce. This one was dated March 31, so it could actually be true. Sad, but true.
My favorite, however, was EMC blogger Barry Burke's post["5773 > c"] explaining howtheir scientists were able to reduce latency on the EMC SRDF disk replication capability:
What the de-dupe team found is that there is a hidden feature within recent generations of this chip that allow a single bit, under certain circumstances, to represent TWO bits of information.Again, this looked real, until I did the math. Start with the speed of light in a vacuum of space ("c" in BarryB's title) which is roughly 300,000 kilometers per second, or put into more understandable units, 300 kilometers per millisecond. However, light travels slower through all other materials, and for fiber optic glass it is only 200 kilometers per millisecond. Sending a block of data across 100km, and then getting a response back that it arrived safely, is a total round-trip distance of 200km, so roughly 1 millisecond. However, EMC SRDF often takes two or three round-trips per write, versus IBM Metro Mirror on the IBM System Storage DS8000 which has got this down to a single round-trip. The number of round-trips has a much bigger effect on latency than EMC's double-bit data compression technique. With IBM, you only experience about 1 millisecond latency per write for every 100km distance between locations, the shortest latency in the industry.
It is good that once a year, you should be skeptical of what you read in the blogosphere, and sometimes check the facts!
technorati tags: April Fools Day, Tim Ferris, 4HWW, outsourcing, Guy Kawasaki, Ruby on Rails, Twitter, Alan Lepofsky, Lotus, Notes, Earth Hour, spam, John Tierney, Ed Begley Jr., milk, carbon dioxide, Wayan Vota, OLPCnews, Windows XO, Gretchen Rubin, Kai Ryssdal, Freakonomics, NPR, Mind Habits, penny, nickel, EMC, BarryB, SRDF, IBM, DS8000, Metro Mirror, latency, fiber optic, speed of light