Re: SCSI vs SATA

[Greg Smith <gsmith(at)gregsmith(dot)com>]

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(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD