5.3: Troubleshoot Storage Devices and RAID Arrays

Storage Failure Symptoms

Indicated by…

• Read/write failure: “Cannot read from source disk”

• Slow performance (lots of LED activity; retry… retry… retry…)

• Loud clicking/grinding/scraping

Disk Failure Troubleshooting

• Backup files

• Check for loose/damaged cables

• Check for overheating

• Check power supply

• Run hard drive diagnostics

Boot Failure Symptoms

Drive not recognized, boot device not found, or OS not found.

Visual signs include: Flashing lights, beep sounds, or error messages

Boot Failure Troubleshooting

Check:

• Cables

• BIOS boot sequence (removable disks or disabled storage interfaces)

• Hardware configurations (for new devices)

• Try the drive in another computer

Data Loss/Corruption

Hard drives eventually fail; SSD may stop working (can read, but can’t write)

Repairs are difficult/expensive and not always successful

Data can be impossible to recover; ALWAYS have a backup

RAID Not Found

Check for missing or faulty RAID controller

RAID stops working

Each RAID config differs—consult system console before pulling drives

RAID 0 failure condition

A single drive failure breaks array and causes data loss

RAID 1 failure condition

Array works as long as AT LEAST ONE drive is operational

RAID 5 failure condition

Array works when AT MOST ONE drive is NOT operational

RAID 10 (1+0) failure condition

Can lose all but one drive from each mirrored set

Self-Monitoring, Analysis, and Reporting Technology

S.M.A.R.T.
Typically third-party tools or built-in OEM diagnostics

S.M.A.R.T. purpose

Schedules disk checks, detects and warns of hardware failures early

Replace the drive immediately

If S.M.A.R.T. warns of a failure…

I/O Operations Per Second (IOPS)

Metric of max performance; useful for comparing storage device access

Hard Drive IOPS

200 IOPS

SSD IOPS

1,000,000 IOPS

Read/Write Operations

Accessing memory, computer bus communication, accessing spinning drives, etc.

Drives Missing in OS

OS boots normally, but other drives aren’t shown; check BIOS first

Unfound Internal/External drives

Drive may be bad, cable disconnected, or no power to drive

Unfound Network Shared Drive

Reconnect drive at sign-in or go through login script to map the drive