Miles V. Aronnax

Adding two more certifications to the pile: Red Hat Certified System Administrator (RHCSA) and Red Hat Certified Engineer (RHCE). I really have to thank my employer, the College of Liberal Arts and Sciences at Iowa State University of Science and Technology for these as the LAS college paid for the tests and the training. (Thanks Arne!)

On All Hallows Eve, I decided to finally take the LPIC-1 exams needed to get my 3-in-1 certification. I'd been studying off and on for the last four or five months so I felt pretty prepared but still slightly nervous. (After all, I had put down around $400 for these tests.)

The scenario: A small but critical file has been deleted from a RAID set. Standard file recovery tools are not viable or don't exist. Can the file still be recovered? Assuming that you know a fragment of the file, and the file is small enough to fit within a stripe, then it may be possible.

In my case, I received a call where someone deleted the last file system snapshot containing the file before realizing it was needed. Luckily, a reasonably unique string within the file was known, and the file was known to be much smaller than the RAID stripe size (128KB) so I set about writing a utility to scan a drive for the string and save all candidate stripes to a separate drive.

Let's say that you run a few hundred CPU-hours to determine some properties of a particular nucleus. When the calculation is done, you get the one bit you care about, say the transition probabilities of the nucleus. Do you delete the other resultant data that you don't need but may still be useful to others? Many people would say "store it", but how? We created a system to do just that.

"A Data Management System for Ab-Initio Nuclear Physics Applications", Fang Liu, Ritu Mundhe, Masha Sosonkina, Chase Cockrell, Miles Aronnax, Pieter Maris and James P. Vary. High Performance Computing Symposium (HPC 2011), Boston, MA, Apr. 3-7, 2011

I'm sure many people recall the Google Labs Aptitude Test question (#10) about an infinite, square lattice of one Ohm resisters. Other people may recall it from this xkcd comic. But in short, the problem is to find the equivalent resistance between two points separated on the grid by a knight's move (as in chess).

The Friday before last I convinced myself that if I could find a pattern to counting the number of simple paths connecting the two points, I could then solve for the effective resistance. After several hours of coding to find the number of paths with seven steps (or edges), I realized I was wrong. However, I still found the problem interesting and hence decided to post the code here.

Ah winter break, is there ever a better time to play with a readily breakable cipher? No, I don't mean Caesar cipher; I mean the next step up--Vigenère's polyalphabetic cipher.