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crash vs. power drop

crash vs. power drop

Posted Sep 14, 2009 15:06 UTC (Mon) by ncm (subscriber, #165)
In reply to: crash vs. power drop by nye
Parent article: POSIX v. reality: A position on O_PONIES

This is where Scott Adams's "Which is more likely" principle is useful. We just frame the question, thus:

Drive manufacturer A can sell almost equally as many drives made this way as that way, but "that way" costs more development time and might make it come out a little slower in benchmarks. Some purchase decisions depend on claiming it's made "that way". The manufacturer can make it "that way" or just say it is, but not. Which is more likely?

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crash vs. power drop

Posted Sep 14, 2009 16:12 UTC (Mon) by nye (guest, #51576) [Link]

A fair point, but in all things there's a strong economic incentive to claim that a product does something it doesn't, if that will make more people buy it, and yet most things don't claim do do something which is simply factually not true.

Usually when it's a feature that either works or doesn't - so it's not a subjective measurement - it's likely that a product does at least technically do what it says it does.

Presumably the argument is that the manufacturers aren't specifically claiming a particular feature, but the disk is behaving in a particular way that just happens to be not what the user expected - so they're not technically lying. This does seem to weaken the idea that they're doing it to improve the chances of people buying it though, if they're not stating it as a feature.

Just out of interest, I've just spent a while trying to see if I can find out what the difference is between the Samsung HE502IJ and HD502IJ - two drives which are identical on paper, but one is sold as 'RAID-class'. Neither are even remotely expensive enough not to lie about their actions, so what's the difference? Well, some forum post claims that one has a 'rotational vibration sensor', whatever that means.

In conclusion, people who try to sell you things are all liars and cheats, and I intend to grow a beard and live out the rest of my days as a hermit, never having to worry about these things again. Perhaps I shall raise yaks.

crash vs. power drop

Posted Sep 15, 2009 12:52 UTC (Tue) by Cato (subscriber, #7643) [Link]

I believe that TLER (time limited error recovery) is one characteristic of enterprise drives - simply means fewer retries so that the RAID controller or OS gets a drive failure more quickly, and knows to use redundancy to complete the I/O.

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