[Beowulf] Re: failure trends in a large disk drive population

Eric Thibodeau kyron at neuralbs.com
Wed Feb 21 19:51:03 EST 2007


Justin,

	Yes, I came across your previous post further down the intertwined thread. One other thing that could have been interesting to see then would be to have monitored _all_ of the system's "health" monitors such as voltage, powersupply fan speed. There may be some other correlations to be made from fluctuating/dying powersupplies... a shot in the dark but all is linked ;)

As for the [censored] GOOGLE_NDA_BOT.... LOL! :) Thanks, that felt good.

Eric
Le mercredi 21 février 2007 18:50, Justin Moore a écrit :
> 
> >> How did they look for predictive models on the SMART data?  It sounds
> >> like they did a fairly linear data decomposition, looking for first
> >> order correlations.  Did they try to e.g. build a neural network on it,
> >> or use fully multivariate methods (ordinary stats can handle it up to
> >> 5-10 variables).
> >>
> >> This is really an extension of David's questions below.  It would be
> >> very interesting to add variables to the problem (if possible) until the
> >> observed correlations resolve (in sufficiently high dimensionality) into
> >> something significantly predictive.  That would be VERY useful.
> >>
> >
> > RGB, good idea, apply clustering/GA/MOGA analisys techniques to all of 
> > this data. Now the question is, will we ever get access to this data? 
> > ;)
> 
> As mentioned in an earlier e-mail (I think) there were 4 SMART variables 
> whose values were strongly correlated with failure, and another 4-6 that 
> were weakly correlated with failure.  However, of all the disks that 
> failed, less than half (around 45%) had ANY of the "strong" signals and 
> another 25% had some of the "weak" signals.  This means that over a 
> third of disks that failed gave no appreciable warning.  Therefore even 
> combining the variables would give no better than a 70% chance of 
> predicting failure.
> 
> To make things worse, many of the "weak" signals were found on a 
> significant number of disks.  For example, among the disks that failed, 
> many had a large number of seek error; however, over 70% of disks in the 
> fleet -- failed and working -- had a large number of seek errors.
> 
> About all I can say beyond what's in the paper is that we're aware of 
> the shortcomings of the existing work and possible paths forward.  In 
> response, we are
> <GOOGLE_NDA_BOT>
> Hello, this is the Google NDA bot.  In our massive trawling of the 
> Internet and other data sources, I have detected a possible violation of 
> the Google NDA.  This has been corrected.  We now return you to your 
> regularly scheduled e-mail.
> [ Continue ]  [ I'm Feeling Confidential ]
> </GOOGLE_NDA_BOT>
> 
> So that's our master plan.  Just don't tell anyone. :)
> -jdm
> 
> P.S. Unfortunately, I doubt that we'll be willing or able to release the 
> raw data behind the disk drive study.
> 
> Department of Computer Science, Duke University, Durham, NC 27708-0129
> Email:	justin at cs.duke.edu
> Web:	http://www.cs.duke.edu/~justin/
> 

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