Back in 2000, Google only had data centers on the US west coast and were planning an expansion over to the east coast, to reduce latency to end users. At the time, Google was not hugely profitable like today, and were very conscious of costs. One of the biggest costs of the move was duplicating the data contained in their search indexes over onto the east coast. Google had just passed indexing 1 billion web pages, and had around 9 terabytes of data contained in their indexes. They calculated that even at the highest speed of 1 Gigabit per second, it would take 20 hours to transfer all the data, with a total cost of $250,000.
Larry and Sergey had a plan however, and it centered on exploiting a loophole in the common billing practice known as burstable billing, which is employed by most large bandwidth suppliers. The common practice is to take a bandwidth usage reading every 5 minutes for the whole month. At the end of the month, the top 5% of usage information is discarded, to eliminate spikes (bursts). They reasoned that if they transferred data for less than 5% of the entire month (e.g. for 30 hours), and didn't use the connection at all outside that time, they should be able to get some free bandwidth.
So for 2 nights a month, between 6pm and 6am pacific time, Google pumped the data from their west coast data center to their new east coast location. Outside of these 2 nights, the router was unplugged. At the end of the month the bill came out to be nothing.
They continued like this every month until the contract with their bandwidth supplier ended, and they were forced to negotiate a new one, which meant actually paying for their bandwidth. By this time, Google had started buying up strategically located stretches of fiber, paving the way for its own fiber network to support its increasing bandwidth needs.
Source:
In The Plex: How Google Thinks, Works, and Shapes Our Lives [Amazon]
By Steven Levy
Published: April 12, 2011
See pages 187-188, Steven Levy's interview with Urs Hölzle and Jim Reese.
Wednesday, February 20, 2013
Saturday, February 2, 2013
How to learn a new programming language
Here's some tips on learning a new programming language. They aren't listed in any specific order. Hopefully you'll gain from this at least one new tip that will help you to become proficient in the next language you learn.
- Build something you actually need right now. This could be either a tool you can use in your day job, or something useful you can make use of at home.
Consider these example projects ...- Write a simple unit testing framework. Many new languages don't have any unit testing frameworks available when they are first introduced. This project will force you to use areas of the language like reflection and meta-programming. Once completed, it becomes useful straight away, for unit testing your future work in the language.
- Implement a disk usage tool; it summarizes the disk usage of all directories on a disk and outputs to the console. It doesn't require overly complex algorithms but touches a lot of the basics: recursion, filesystems, command line parsing and output formatting.
- Implement a backup/archive script which has command line switches to exclude certain file extensions. It should place the backup into a single .zip or .tar.gz file. The project will touch on the following: recursion, filesystems, command line parsing, compression libraries and regular expressions.
- Port an existing, well known program to the new language. Since you are porting it, you already have the application design work done. This frees up your mind to focus on the specifics of the new language. After you've finished you'll then have a good reference to which you can refer back to, when comparing the old with the new language.
- Find a decent book on the language and read through it all as fast as you can. The goal is not to memorize everything, but to soak up the ideas and idioms of the language. Then write some small but non-trivial project. When you get stuck, hopefully it'll trigger a memory of something from the book, and you can go back to refer to it.
Many of the "in a Nutshell" and "Head First" series of books, both published by O'Reilly, are highly rated by readers - they are available for many popular languages (C, C++, C#, Java, Python, JavaScript, PHP). - Mix action with equal parts learning (reading books/tutorials). Too much action without learning, and you get a lot of poor quality code. Too much learning without enough action, and you fail to absorb the material to a deep enough level.
- Study reference works on public repositories. Find a medium sized project on GitHub which is written 100% in the language. Read though the code and try to understand it. Look for projects written by the language designers or an acknowledged expert.
As an example, with Go, the standard libraries for the language are written in Go and are open source, e.g. here is part of the strings package. In addition, Brad Fitzpatrick and other members of the Go team have several projects on GitHub that you can read and learn from, e.g. here is a Go client for Memcache. - Devote large, uninterrupted chunks of time, at least half a day, to learning the new language. Brief, half hour sessions over the course of the week aren’t really useful, because most of the time would be spent just getting back up to speed on what you previously studied.
- Learning a language shouldn’t just be a solitary endeavor. There are plenty of people who have made the same mistakes that you have, so asking for help is a great way to overcome problems when you get stuck. Some possible sources of help online: Language-specific IRC channels, StackOverflow, Twitter, Facebook groups, Quora, Google+, Google groups. You can also submit your finished code to these forums after you've completed a project; people more experienced with the language than you will often be able to identify areas which can be improved or simplified.
- Use an editor with syntax highlighting. Perennial favorites such as Vim and Emacs, plus newer editors such as Sublime Text, feature support for most if not all programming languages and are available for all major operating systems. Some languages are often associated with specific IDEs; these are a good idea when learning a new language. These are generally ...
- Eclipse IDE for Java and Android development.
- Xcode for Objective-C and iOS development (on Mac OSX only).
- Visual Studio IDE for C#, C++, VB.NET, F# (on Windows only).
- Working on a real project with real customers and deadlines is a white hot crucible for learning a new programming language. If you really need to learn a language quickly, then consider taking on a new job which requires it. Once you've got the job, you'll have no other choice but to learn it quickly.
- Finally, a tip from The Pragmatic Programmer, Tip #8 "Invest Regularly in Your Knowledge Portfolio":
"Learn at least one new language every year. Different languages solve the same problems in different ways. By learning several different approaches, you can help broaden your thinking and avoid getting stuck in a rut. Additionally, learning many languages is far easier now, thanks to the wealth of freely available software on the Internet."
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