How to Monitor and Predict Disk Health with SMART and smartctl

Background Introduction

Disk is a critical data carrier; failure reduces capacity and can cause downtime. Besides clustering and disaster recovery, monitoring and predicting disk health is essential.

SMART Overview

SMART (Self‑Monitoring Analysis and Reporting Technology) is an automatic HDD/SSD health detection and warning system that compares measured parameters against manufacturer‑defined thresholds and can issue alerts.

smartctl Tool

smartctl, part of smartmontools, is the Linux command‑line utility for retrieving SMART data. Install on CentOS with yum install smartmontools . It works with RAID controllers, NVMe, and other PCI‑E disks. smartd can run scheduled checks and send email alerts.

Discovering Disks

Use fdisk -l to list disks, but on RAID‑connected devices you must specify the device type, e.g. smartctl -a /dev/sdX may not work. smartctl supports reading SMART data through RAID cards using the -d option.

Example for a Dell PERC H710 (LSI MegaRAID):

smartctl -? /dev/sda -d sat+megaraid,0

smartctl Parameters

-h Show help

-i Show basic device information

-a Show all SMART attributes

-x Show all device information

-d Set device type (ata, scsi, sat, etc.)

-s Enable/disable SMART

SMART Metrics

Typical SMART attributes (example from an Intel 520 SSD) include:

ID 0x01 – Read Error Rate : Underlying data read error rate.

ID 0x05 – Reallocated Sector Count : Number of sectors remapped to spare area.

ID 0x09 – Power‑On Hours : Total powered‑on time.

ID 0xBC – Command Timeout : Count of aborted commands, often zero.

ID 0xC4 – Reallocation Event Count : Events of sector reallocation.

ID 0xC5 – Current Pending Sector Count : Unstable sectors awaiting reallocation.

ID 0xC6 – Uncorrectable Sector Count : Sectors that cannot be corrected.

SMART Values

VALUE : Normalized current value (1‑253, higher is better).

THRESH : Manufacturer‑defined threshold.

WORST : Worst recorded value.

RAW_VALUE : Raw measurement, may need conversion.

Comparison of VALUE, WORST and THRESH determines the health status (normal, warning, failure).

Information Collection and Alerting

SMART data varies by vendor; a database (e.g., /var/lib/smartmontools/drivedb/drivedb.h ) maps model‑specific IDs to meanings. Scripts can enumerate disks, detect RAID/NVMe, invoke smartctl with appropriate -d options, store results, and trigger alerts for pre‑fail attributes, high wear, or FAILED status.

Automation can be done with smartd or a custom scheduler (e.g., qcmd) that runs smartctl across machines, aggregates data, and sends notifications via email, SMS, or app messages.

Summary

Disk storage is a key hardware component; using SMART technology allows proactive detection of failures, reducing operational pressure. At large scale, collected SMART metrics can inform procurement, predict lifespan, and improve service reliability.