SMART is an early-warning aid, not a guarantee that a drive is safe or a countdown to failure. Some SMART signals have been associated with higher failure rates across large drive populations, but a healthy status cannot rule out failure and the data alone cannot reliably predict when an individual drive will fail. Keep an independent backup, and treat concerning reports as a reason to protect your files and investigate.
What SMART status means
SMART—Self-Monitoring, Analysis and Reporting Technology—is supported by many modern ATA, SCSI and NVMe storage devices. Compatible utilities, including smartmontools, can read the status, attributes, logs and test information a device exposes. What is available depends on the drive and how it is connected.
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A status such as “healthy” or “passed” is a report from the device and tool, not a promise about the drive’s future. It does not mean that every failure mode has been detected, nor does it provide a dependable estimate of remaining life.
Can SMART data predict hard drive failure?
SMART can contribute useful warning signals, but it does not reliably forecast failure for an individual drive. The key evidence often cited is a 2007 study by Eduardo Pinheiro, Wolf-Dietrich Weber and Luiz André Barroso. They analyzed more than 100,000 consumer-grade drives used in Google’s professionally managed data centers. The data covered December 2005 through August 2006, so the results describe that fleet and period—not a current probability estimate for every consumer drive.
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In that population, a drive was 39 times more likely to fail within 60 days after its first scan error than drives with no such errors. First errors in reallocation, offline reallocation and “probational” counts also correlated with higher failure probability. These are associations observed across the study population; they are not an individual drive’s odds or a prediction that a particular drive will fail within 60 days.
The study also shows why a missing warning is not reassurance. More than 56% of failed drives had none of the four strong signals the authors examined: scan errors, reallocation counts, offline reallocation counts and probational counts. When they considered other SMART parameters (excluding temperature), more than 36% of failed drives still had zero counts on all variables considered. The authors concluded that models based on SMART parameters alone were unlikely to be useful for predicting individual drive failures. Read the full FAST 2007 paper or its Google Research abstract.
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Which SMART attributes can be warning signals?
The strongest examples in the cited study were scan errors, reallocation, offline reallocation and probational counts. A concerning value or a worsening trend in a relevant attribute may justify checking the drive and protecting data, but no single attribute proves that failure is imminent.
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- Reallocation-related counts: The study found that first errors in reallocation and offline reallocation counts correlated with higher failure probability in its fleet.
- Scan errors: The first scan error was associated with a substantially higher failure rate in the study, but that relationship should not be translated into a personal forecast.
- Other raw values: Their meanings and reporting can vary by device and model. Avoid treating generic internet threshold charts as universal; consult model-specific documentation and the tool’s report.
Backblaze also publishes raw fleet data examining SMART attributes and failure rates, collected using smartmontools. Such fleet analysis can reveal population-level relationships, not a universal threshold or a forecast for your particular drive. See Backblaze’s SMART stats and failure rates.
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Can a hard drive fail if SMART says it is healthy?
Yes. The Google study found that many failed drives had no count in the four strong signals analyzed. SMART can report only the information a device exposes, and a clean status cannot certify that a drive will keep working. Do not wait for a warning—or try to infer a failure date—before backing up important files.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What to do when SMART reports a problem
- Protect important files first. Make sure you have a separate backup rather than relying on the drive being monitored. SMART monitoring is not a backup.
- Review the complete report. Use a compatible utility such as smartmontools and note the drive model, interface, reported attributes, logs and test results. Device support and available fields vary.
- Investigate the specific drive. Check model-specific documentation and consider whether errors or counts are changing over time. A single raw value should not be interpreted using an assumed universal threshold.
- Do not use a clean status to postpone protection. If the data matters, keep the independent backup current even when SMART reports no warning.
The 2007 study found little correlation between failure rates and elevated temperature or activity levels in its deployment. That finding does not override a manufacturer’s operating limits or establish that cooling is unimportant; it applies to the study’s population and methods.
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What SMART evidence cannot establish
- A precise remaining lifespan or individual failure date.
- A universal failure probability for today’s consumer drives based on the 2005–2006 Google fleet.
- A single cross-vendor interpretation for every raw attribute or threshold.
- Safety merely because the overall status is reported as healthy.
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