One problem with fully understanding SMART stats, Budman said, is that drive manufacturers don't share specific details of use cases for them.
"If you look at the Wikipedia entry for SMART stat 1, for example, it says 'vendor specific' value. Seagate wants to track something, but only they know what that is. Western Digital uses SMART for something else - neither will tell you what it is," Budman said.
"SMART 1 might seem correlated to drive failure rates, but actually it's more of an indication that different drive vendors are using it themselves for different things," he added.
Budman pointed to SMART stat 12 as another example of a metric that should indicate an impending drive failure but doesn't. SMART 12 relates to how many times a drive is powered up, which should correlate to long-term wear. At first, Budman said, the annual failure rate seemed to go up related to SMART 12 alerts, but then the failure rates leveled off and actually went down.
"So at first it looks correlated but it's not. It doesn't have a linear progression," he said. "Whatever indicator they put in there [the SMART firmware], it is not consistent."
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