Objective 5.3: Given a scenario, troubleshoot drive and RAID issues

Cert: CompTIA A+ Core 1 (220-1201) V15 Domain: 5.0 Hardware and Network Troubleshooting Weight: ~28% of Core 1 (largest domain) Depth: Given a scenario, troubleshoot. Recognize symptoms and apply remediation for storage and RAID issues.

What this objective tests

You should recognize storage symptoms (LED indicators, audible signs of failure, performance and capacity errors, RAID-specific alerts) and know the right next steps for each.

Key facts

LED status indicators:

• Most drive bays and RAID controllers have LEDs that signal drive activity and faults. Green/blue typically means OK or active; amber/red means fault, missing, or rebuilding. Always check the LED state before opening the chassis.

Grinding or clicking sounds:

• Grinding. Usually mechanical wear in an HDD spindle or actuator. Imminent failure.
• Clicking (the "click of death"). HDD read/write head failing to find tracks. Imminent failure. Save data immediately.

Boot symptoms:

• Bootable device not found. BIOS cannot find a bootable OS. Could be missing/disconnected drive, drive failure, corrupted boot sector, or wrong boot order.
• Data loss / corruption. Files missing or corrupted. Could be drive failure, filesystem corruption, malware, or human error.

RAID-specific symptoms:

• RAID failure. A drive in the array has failed. RAID 1/5/6/10 continue operating in degraded mode but with no further fault tolerance until rebuild completes.
• Array missing. The entire RAID array is no longer visible. Could be controller failure, multiple-drive failure beyond the array's tolerance, or RAID configuration loss.
• Audible alarms. Most RAID controllers emit a constant tone when a drive fails or the array degrades. Acknowledge and investigate immediately; the alarm itself is not the failure.

Health monitoring:

• S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology). Drives report internal health metrics: reallocated sectors, read errors, temperature, power-on hours. A S.M.A.R.T. warning is a heads-up that the drive is failing; replace before it fails fully.
• Extended read/write times. Operations that should be fast are now slow. Often the drive remapping bad sectors, which precedes total failure.
• Low performance IOPS. Specifically relevant for SSDs and storage arrays where IOPS (input/output operations per second) is the key metric. Drops indicate failing drives, controller issues, or array stress.

Missing drives in OS:

• A drive shows in BIOS but not in the OS, or vice versa. Could be filesystem damage, cable issues, drive controller failure, or a permission/mount issue.

Diagnostic approach

1. Listen for grinding or clicking. Stop the drive if it's still spinning and back up data immediately.
2. Check LEDs on the drive bay or RAID controller.
3. Read S.M.A.R.T. data via OS tools (CrystalDiskInfo, smartctl on Linux/macOS) or the RAID controller's management interface.
4. Check BIOS to see if the drive is detected.
5. Check OS Disk Management or equivalent for partition and filesystem status.
6. For RAID: check the controller's UI for array status, drive status, rebuild progress.
7. For data recovery: stop using the drive if possible. Forensic recovery is easier on a quiesced drive than on one still being written.

Common gotchas

• Don't rebuild a RAID without backups. Rebuilding stresses the surviving drives. If a second drive is on the edge of failure, the rebuild can finish the job. Always have backups before rebuilding.
• S.M.A.R.T. is not perfect. A drive can fail without S.M.A.R.T. warnings. Conversely, S.M.A.R.T. can flag drives that keep running for months. Use it as one signal, not the only signal.
• Boot order vs missing drive. A "bootable device not found" message can mean the BIOS boot order changed (new USB plugged in first) rather than the drive failing.
• Loose SATA cable. Common cause of intermittent drive issues. Reseat both ends.
• Cloning a failing drive. Use specialized tools that tolerate read errors (ddrescue, HDD Regenerator, vendor utilities). A normal clone aborts on the first bad sector.
• RAID 5 rebuild risk on large drives. A rebuild on multi-TB drives can take days. Second drive failures during rebuild are the most common total-array-loss event. Consider RAID 6 or RAID 10 for large drives.
• Array missing after controller swap. Different RAID controllers store metadata differently. Swapping a controller across vendors can lose the array configuration even though all drives are intact.

Real-world context

For SMB Revtek customers:

• Backups first. RAID is for availability. Backup is for data protection. These are different concerns.
• Monitor S.M.A.R.T. on every drive (especially NAS, file servers). Replace warning drives proactively.
• Have spare drives on the shelf for any production RAID. Rebuild as soon as a drive fails.
• Test backup restores quarterly. A backup you cannot restore is no backup at all.

Common helpdesk calls:

• "My computer is slow at saving files." Check drive health. Often a dying HDD remapping sectors.
• "It says no boot device." Check BIOS, drive presence, boot order, cables.
• "The server alarm is going off." A drive in the array failed. Acknowledge, replace, monitor rebuild.
• "I deleted a file by accident." Check Recycle Bin, then backups. Never run recovery tools against a failing drive without imaging it first.

Sources

• [CompTIA A+ 220-1201 Exam Objectives Version 4.0, Section 5.2](../../../../../../30-RevyTechJourney/CompTIA%20A%2B%20220-1201%20Exam%20Objectives%20%284.0%29.pdf)
• [Wikipedia: S.M.A.R.T.](https://en.wikipedia.org/wiki/S.M.A.R.T.)
• [Wikipedia: Standard RAID levels](https://en.wikipedia.org/wiki/Standard_RAID_levels)
• [Wikipedia: Hard disk drive failure](https://en.wikipedia.org/wiki/Hard_disk_drive_failure)
• [Microsoft Learn: Storage troubleshooting](https://learn.microsoft.com/en-us/troubleshoot/windows-server/backup-and-storage/storage-resources)