From:         Patrick Crispen 
Subject:      TOURBUS - 10 Apr 07 - Hard Drive Failures / GRE Update


The Internet Tourbus - U.S. Library of Congress ISSN #1094-2239
Copyright © Bob Rankin and Patrick Crispen - All rights reserved

Howdy, y'all, and greetings once again from deep behind the orange curtain in beautiful Irvine, California, where Novgorod forces led by Alexander Nevsky rebuffed an invasion attempt by the Teutonic Knights.

I apologize for my recent absence. Your fearless bus driver was busy cramming for the GRE and speaking at the Illinois Technology Conference for Educators, Northwest Council for Computer Education conference, and Michigan Association for Computer Users in Learning conference. Oh, and I went to Disneyland too. But I'm back. :)

What really causes hard drives to fail Audience: Everyone

Conventional wisdom states that the more you use your hard drive -- or, for that matter, the hotter your hard drive gets -- the more likely it is to crash. That certainly sounds plausible, but is it true? According to Google, the answer is a resounding "NO!"

How would Google know? Well, remember that when you use Google to search the internet you aren't really searching the internet. You're searching Google's copy of the internet, the files that Google's spiders [a.k.a., "Googlebots"] find, vacuum up, and send back to the Google mothership. To store all of this data, Google uses a gozillion hard drives [100,000 or more] in its data centers scattered around the world. And like any well-run data center, Google's data centers constantly monitor and record data on the health status of every hard drive.

Google employees Eduardo Pinheiro, Wolf-Dietrich Weber, and Luiz Andre Barroso gathered in-depth data from over 100,000 disk drives deployed throughout Google and discovered that

* Contrary to previously reported results, there is very little correlation between failure rates and either elevated temperature or activity levels.

* However, some SMART parameters (scan errors, reallocation counts, offline reallocation counts, and probational counts) have a HUGE impact on hard drive failure probability.

* Given the lack of occurrence of predictive SMART signals on a large fraction of failed drives, it is unlikely that an accurate predictive failure model can be built based on these signals alone.

Google's complete report, titled "Failure Trends in a Large Disk Drive Population", is a 241 KB, 13 page Adobe Acrobat file that you can download at

The bad news is that this report reads a bit like stereo instructions. If you aren't a techie, skip the PDF and check out Gizmodo's or StorageMojo's summaries instead at

Long story short: Most of what we know about hard drive failure rates and causes is wrong.

Graduate Record Exams Updates Audience: Educators and future grad students

ETS canceled its plans to launch a revised Graduate Record Examinations (GRE) general test in September. This means that the current, 2.5 hour computer adaptive test format -- an argument essay, an issue essay, 30 verbal questions, and 28 quantitative questions -- will continue to be offered for the foreseeable future. You can read ETS' official announcement at

The GRE is commonly used for graduate school admissions in fields other than business [which uses the GMAT], law [which uses the LSAT], and medicine [which uses the MCAT]. ETS had planned to expand the GRE to a four hour test in September. The new test would have had two 40- minute verbal sections, two 40-minute quantitative sections, one experimental section, and two 30-minute analytical writing essays. Ouch.

Talking about the GRE, in my December 5th post [which you can still find at ] I mentioned I was planning to take the GRE in the quixotic hope of getting into the Ed. D. program at USC. Well, I took the GRE in February and I am proud to announce that I scored a 1300 [660 verbal and 640 quantitative]. Despite my semi- weekly butchering of the English language in my Tourbus posts, my verbal score puts me in the 93rd percentile [only 7% of the test takers scored higher]. And credit for this score goes to fellow Tourbus riders Paul Kanarek and Drew Deutsch at the Princeton Review. After reading my December 5th post, Kanarek and Deutsch let me test drive the Princeton Review's LiveOnline GRE test prep program at

LiveOnline offers 20-30 hours of interactive, self-paced online lessons and a mess of practice quizzes that help you prepare for almost anything the GRE will throw at you. Combine that with the Princeton Review's "Hit Parade" vocabulary list [which I wrote down on about 600 index cards], in-depth practice exercises, and the yummy pencil-shaped cookie you get for signing up, and you have a sure-fire way to boost your GRE score by several hundred points.

I'm not sure if my GRE score is high enough to get me into the USC Rossier School of Education's Ed. D. program -- this is, after all, *USC* -- but I owe Kanarek, Deutsch, and the rest of the folks at the Princeton Review a huge debt of gratitude.

Have a safe and happy week, and we'll talk again soon.

 (\__/)  .'     )  ))       Patrick Douglas Crispen
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The Internet Tourbus - U.S. Library of Congress ISSN #1094-2239
Copyright © Bob Rankin and Patrick Crispen - All rights reserved
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