Which SMART Hard Drive Numbers Translate Into Real Failures?

Image: Ty Nigh / Flickr

If you know a thing or two about hard drives, you're likely aware of SMART, or Self-Monitoring Analysis and Reporting Technology. All modern drives come equipped with this functionality, but taking the statistics it provides and predicting an actual drive failure? Fortunately, data backup firm Backblaze has real-world data to play with and as such, a solid understanding of how SMART factors into drive reliability.

Backblaze's Andy Klein has penned a blog post summarising the company's SMART observations, based on its 67,800-drive data centre in the US.

In Klein's opinion, the most important numbers to look at are:

  • SMART 5: Reallocated Sectors Count
  • SMART 187: Reported Uncorrectable Errors
  • SMART 188: Command Timeout
  • SMART 197: Current Pending Sector Count
  • SMART 198: Uncorrectable Sector Count

Using just these stats alone, Klein says the company has been able to determine with great accuracy which drives are destined for the electronic graveyard:

Operational drives with one or more of our five SMART stats greater than zero — 4.2% Failed drives with one or more of our five SMART stats greater than zero — 76.7%

Even though Klein points out that 23.3 per cent died with "no warning" from SMART, that's still a pretty good hit rate.

The article goes into more detail about other stats you can look at; just hit up the BackBlaze link below.

What SMART Stats Tell Us About Hard Drives [Backblaze]


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