1) Fundamentals: What is HDD storage?

Mechanical hard drives store data on magnetic plates that rotate at high speed, with read/write heads driven by an actuator. Reliability depends on physical wear, vibration, temperature and quality of read/writing operations.

Key concepts include sectors, trails, cylinders and clusters, as well as SMART attributes that help infer the health of the disk. Even with ECC and internal redundancy, physical failures can prevent data reading;

In continued workloads, the failure rate increases over time. Therefore, designing with redundancy and monitoring is essential to avoid losses.

2) What does “I broke 3 HDs” mean? Scenario and signs

In this report, I witnessed failures in three HDs for different causes: natural wear, mechanical impact and control failure. Each disc presented similar symptoms in a progressive way: extreme slowness, reading of unavailable sectors and, finally, unavailability of the volume.

Observed signs: sudden variations in smart attributes such as reallocated_sector_ct, current_pending_sector and SEEK_ERROR_RATE; mechanical noises (clicks, creaks); Performance drops during I/O operations.

Impact: Part of the data was already out of recent backup, requiring quick decisions about partial recovery versus volume reconstruction based on business priorities.

3) Diagnosis and recovery: practical methodology

My approach was to preserve what was left, to minimize additional damage and safely extract data. The rule: Do not write on the defective disk until you have a stable and reliable image for recovery.

Tools and steps used:

• Check SMART and system logs to understand the type of failure;
• Create an area recovery image with a greater chance of readability;
• Validate the integrity of the recovered data, prioritizing critical items.

Note: Each case is unique. In scenarios with visible mechanical damage, it may be necessary to resort to specialized services with a clean bench for physical data recovery.

#!/bin/bash
# Basic Smart Monitor to alert you of potential failures
disks=$(lsblk -dno name)
threshold=5

for d in $disks; of
smartctl -h /dev/$d >/dev/null 2>&1
if[ $? -ne 0 ]; then
echo "[$(date)]smartctl not available in /dev/$d" >&2
continue
phi
Temper=$(smartctl -a /dev/$d | awk/temperature_celsius/{print $10}| head -n1)
crit=$(smartctl -a /dev/$d | awk/current_pending_sector|reallocated_sector_ct/{print $10}| tr\n)

# Simple verification example
if[ -n "$CRIT" ]&&[ "$CRIT" -ge "$THRESHOLD" ]; then
echo "Alert: disk /dev/$d with critical sectors: $crit; temperature: ${temper}c"
phi
done

4) Prevention, architecture and good practices

Storage Planning: Adopt adequate redundancy (RAID 1/5/6/10, ZFS with health check) and 3-2-1 backups to reduce the unavailability window.

Continuous monitoring: usage metrics, temperature, vibration and SMART attributes should trigger alerts. Automate snapshots, consistency check and notifications to the team.

Hardware and Environment: Choose discs designed for workload, ensure stable cooling, vibration control and reliable power supply. Consider using hot spares and load rotation to balance wear.

Recovery Processes: Have a playbook with contacts, deadlines and success criteria. This practice reduces downtime and increases the chances of full or partial recovery depending on the scenario.