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Various databases and how they scale

By chance I stumbled upon an article about databases and how they scale. It's a great read and does an excellent job describing the various stengths and weaknesses regarding different kinds of scaling for databases. Especially the images really capture the essence. Screenshot from 2014-05-09 12:31:57

Think Bayes: Bayesian Statistics in Python

There's a free download available of "Think Bayes – Bayesian Statistics in Python" over at A small excerpt from the book:

The premise of this book, and the other books in the Think X series, is that if you know
how to program, you can use that skill to learn other topics.

Most books on Bayesian statistics use mathematical notation and present ideas in terms
of mathematical concepts like calculus. This book uses Python code instead of math,
and discrete approximations instead of continuous mathematics. As a result, what
would be an integral in a math book becomes a summation, and most operations on
probability distributions are simple loops.

MobaXterm – (Free) All-in-one Xserver/SSH/Linux environment for Windows

I recently stumbled on MobaXterm. It's a complete unix enviroment including X Server/SSH/Telnet/SCP/FTP client all in one. The list of features is impressive to say the least. This is an excellent replacement for Putty.

A small selection of the most useful features:

  • Free. What more is there to say?
  • Tabs and Horizontal / Vertical split panels finally bring the full power of native Unix/Linux terminal emulators to Windows
  • Integrated X server. MobaXterm comes with an integrated X Server. Everything is set up correctly out-of-the-box. X11 forwarding means you can simply SSH to a remote machine and start X11 programs. It supports displaying remote X11 windows as native windows or you can run the X Server ina separate tab/window.
  • Session Management makes it easy to quickly connect to the machine you want.
  • Integrated SFTP when SSHing to a remote machine means you don't have to start a separate SFTP/SCP session. Just browse, upload and download remote files from the left side of the SSH session.
  • Many supported services, such as SSH, Telnet, local Linux/Cygwin terminal, local Windows command prompt, RSH, XDMCP, RDP, VNC, FTP, etc.
  • Session multiplexing provides a quick method of running commands on multiple machines at the same time.
  • SSH bouncing through a gateway SSH server means no more SSHing from machine to machine.
  • Cygwin environment so you can actually get some work done natively on Windows. Batteries, bells, whistles and kitchen sinks (as well as games) included: full unix environment with tools like grep, find, vim, etc, etc, etc.

There are countless more features. This is the terminal emulator app I always hoped Putty would become. Of all the different shells around Putty, separate SSH connection managers and terminals I've tried, this is by far the best one.

Pocket: consume all content offline on your mobile device

My smartphone doesn't have a data plan because the last thing I want is to be able to check my email and facebook while I'm not behind my PC. I do like to read though, so I want to use my smartphone to read content I've previously somehow flagged as interesting.

I've tried many apps. Instapaper, Diigo, Readability and a few others. All of them suck.

Some suck because they don't include inline images from articles in the offline version. Some suck because they're not free, some suck because the don't extract just the article text but make the entire webpage available offline, which doesn't really work on my tiny screen. Others suck because they don't sync properly.

And then there was Pocket. It includes inline images in the offline version, but it doesn't include the rest of a webpage. If it can't reliably detect where the article starts or ends, it makes the entire page available offline. Even on my tiny screen, it still manages to make offline webpages very readable. It's free, and it has no limits on how many articles you can make available offline. It can also make images and videos available for offline viewing.

Pocket is by far the best option for reading offline content on your smartphone / tablet. Get it here, you won't be disappointed.

Read the POSIX standard

Stop reading your local manual pages when programming/scripting stuff, and use the POSIX standard instead:

Online POSIX 2008 (EEE Std 1003.1-2008) standard

There are four main parts:

Some Do's and Dont's:

Finally, read Bash Pitfalls to learn why your shell scripting sucks.

Filesystem Latency

There's an interesting on-going series of articles on file system latency over at Brendan's Blog. Usually when system administrators look into I/O performance, we look at the I/O of the disks. This is usually fine for a rough estimate of raw disk performance, but there's a lot more going on between the actual application and the disk: buffers, cache, the file system, etc. Brendan goes into detail regarding these matters by examining I/O performance of a MySQL database at both the disk and file system level:

This is why I don't use Apple products or DRM media

This company is going out of business because they put all their eggs in a very delicate and quite frankly evil basket:

BeamItDown Software and the iFlow Reader will cease operations as of May 31, 2011. We absolutely do not want to do this, but Apple has made it completely impossible for anyone but Apple to make a profit selling contemporary ebooks on any iOS device.

If you're a company, and you do this:

We bet everything on Apple and iOS and then Apple killed us by changing the rules in the middle of the game.

you need to have your head examined :-) This is not the first time this has happened, and it will most certainly not be the last time. Apple will do anything it can to make a buck over other company's back!

Not just the company is being royally screwed over by Apple:

Many of you have purchased books and would like to keep them. You may still be able to read them using iFlow Reader although we cannot guarantee that it will work beyond May 31, 2011 […] your computer which will let you access them with Adobe Digital Editions or any other ebook application that is compatible with Adobe DRM protected epubs.

So iFlowReader's have probably also lost all their ebooks because they had DRM on them. DRM (Digital Rights Management) is a technology which restricts media to a certain application or device; opening it in third-party applications is usually impossible.

And that's why I have never and will never buy an Apple product, or use any media that is DRM protected.

Einstein for everyone

Lecture notes on the work of Einstein and physics inspired by Einstein's work:

The course is aimed at people who have a strong sense that what Einstein did changed everything. However they do not know enough physics to understand what he did and why it was so important. The course presents just enough of Einstein's physics to give students an independent sense of what he achieved and what he did not achieve.

Easy way to create a Debian package and repository

Interesting article over at

This article describes a simple way on how to create a home made debian package and include it into a local package repository. Although we could use a existing Debian/Ubuntu package, we will start from scratch by creating our own minimalistic unofficial debian package. Once our package is ready, we will include it into our local package repository. This article illustrates very simplistic approach of creating debian package, however it may serve as a template in many different scenarios.

Regular expression Denial of Service (ReDoS)

It's only logical, but I hadn't really thought about it much. Turns out Regular Expression can be vulnerable to external Denial of Service attacks.