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Re: SCSI vs SATA



On Thu, 5 Apr 2007, Scott Marlowe wrote:

On Thu, 2007-04-05 at 14:30, James Mansion wrote:
Can you cite any statistical evidence for this?
Logic?

OK, everyone who hasn't already needs to read the Google and CMU papers. I'll even provide links for you:

http://www.cs.cmu.edu/~bianca/fast07.pdf
http://labs.google.com/papers/disk_failures.pdf

There are several things their data suggests that are completely at odds with the lore suggested by traditional logic-based thinking in this area. Section 3.4 of Google's paper basically disproves that "mechanical devices have decreasing MTBF when run in hotter environments" applies to hard drives in the normal range they're operated in. Your comments about server hard drives being rated to higher temperatures is helpful, but conclusions drawn from just thinking about something I don't trust when they conflict with statistics to the contrary.

I don't want to believe everything they suggest, but enough of it matches my experience that I find it difficult to dismiss the rest. For example, I scan all my drives for reallocated sectors, and the minute there's a single one I get e-mailed about it and get all the data off that drive pronto. This has saved me from a complete failure that happened within the next day on multiple occasions.

The main thing I wish they'd published is breaking some of the statistics down by drive manufacturer. For example, they suggest a significant number of drive failures were not predicted by SMART. I've seen plenty of drives where the SMART reporting was spotty at best (yes, I'm talking about you, Maxtor) and wouldn't be surprised that they were quiet right up to their bitter (and frequent) end. I'm not sure how that factor may have skewed this particular bit of data.

--
* Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD


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