CompTIA A+ Core Certification: The Basics of Hardware and Network Troubleshooting - Troubleshooting Storage Drives and RAID Arrays

220-1101: Objective 5.3: Given a scenario, troubleshoot and diagnose problems with storage drives and RAID arrays.
Problems with mass storage devices are among the most frightening to a business or an individual. The tips and techniques in this section can help solve problems and make data recovery possible.
The sections that follow present common symptoms a technical support specialist might encounter when summoned for help with failing hard drives.
Light-Emitting Diode (LED) Status Indicators
Using light-emitting diode (LED) status indicators, a technician can evaluate a computer’s health at a glance. Computers, switches, routers, and other devices all use LEDs to visually communicate their activity status or any issues with communication. As with the beeps and boops of startup error codes, LEDs communicate in code as well.
Different devices also have color codes for their indicators. Table 5-4 lists examples of LEDs and their meanings.

Table: LED Status Indications




































 

Of course, the availability of lights and the meaning of the codes varies among manufacturers, so accessing the documentation might be necessary to understand the complete situation.
Notice that, for hard drives and RAID arrays, the LED signals indicate only activity or inactivity; the technician must interpret them to understand if there is a problem. A technician should know what normal benchmark activity looks like and then troubleshoot if there is a change from the benchmark. For example, if the LEDs for a RAID array start flickering incessantly and showing activity even when there is no real load on the machine, it could indicate that the RAID is misconfigured and is working too hard to keep redundant memory updated. The same is true for a hard drive. Flickering lights could mean that background activities such as swap files are working harder than they should, and settings might need to be readjusted or upgrades need to be considered.
Read/Write Failure
Read/write failures can take place for a number of reasons, including the following:
- Physical damage to the drive: Dropping any magnetic storage drive can cause damage to read/write heads and platters. The drive might start to make noise or might not spin up at all.
- Damaged cables: SATA cables are often included with new motherboards and are inexpensive to purchase. Swapping cables is an easy first step that often solves problems.
- Damaged SATA host adapter on motherboard: Most late-model motherboards have several SATA ports; if swapping a SATA cable does not solve a problem, use the original cable in a different SATA port on the motherboard.
- Overheated hard disk: The faster a hard disk turns (that is, the higher the RPM), the more likely it is that overheating will take place, especially if airflow is restricted. To prevent overheating, install a cooling fan in front of the 3.5-inch drive bays used for a hard disk(s) and make sure it pulls air into the PC. If you have two or more drives stacked on top of each other with limited airflow, move drives to other drive bays to improve airflow.
- Overheated CPU or chipset: Overheated CPU, chipset, or other components can cause read/write failures. Double-check case fans, the power supply fan, and the CPU and chipset heat sinks. Remove dust and dirt from air intakes and fans. Remove loose or failed heat sinks, remove old thermal grease, and reassemble them with properly applied thermal grease.
Slow Performance
Although SATA drives can manifest slow performance, the causes and solutions for each type of drive vary widely.
To improve slow performance with SATA hard disks, look for these problems:
- Reduced-performance configuration of 3Gbps or 6Gbps drives: Some 3Gbps and 6Gbps SATA drives are jumpered to run at the next slower rate, to enable compatibility with older host adapters. Remove the speed-reduction jumper when it is not needed; see the drive documentation for details. Figure 5-14 illustrates a jumper on a 3Gbps drive that limits its performance to 1.5Gbps.
- Using a 3Gbps cable with a 6Gbps drive and host adapter: SATA cables made for 6Gbps drives can also be used with slower speeds.
- SATA host adapter configured for IDE or emulation mode: SATA host adapters can be configured by the system BIOS (conventional or UEFI) to run in IDE (emulation) mode, RAID mode, or AHCI mode. Use AHCI mode to enable full performance because this mode supports native command queuing (NCQ) and other advanced features.
- SATA host adapter configured to run at reduced speed: SATA host adapters on some systems can be configured to run at different speeds, such as 6.0Gbps, 3.0Gbps, or Auto. Select 6.0Gbps when using a 6.0Gbps drive and cabling. To enable the drive and host adapter to autonegotiate the correct speed, select Auto.


To Run This Drive at Its Designed 3.0Gbps Interface Speed, Remove the Jumper

Note: Some SATA drives use a configuration jumper to permit Power-Up in Standby (PUIS) mode. Before you remove a jumper block from a SATA hard disk, check the drive’s documentation at the vendor’s website. Some drives are marked with incorrect jumper block legends.
To improve slow performance with SSDs, look for the following issues:
- The drive is connected to a slow SATA host adapter: Early SSDs were designed for 3Gbps SATA interfaces, but most recent models support the faster 6Gbps interface. When using an SSD on a system with a mixture of 3Gbps and 6Gbps SATA ports, be sure to use the 6Gbps ports.
- The partition might be misaligned: Windows automatically creates the first partition on an SSD so that it is on a page boundary, to provide maximum performance. However, if you do not use the entire SSD for a single partition, additional partitions might be misaligned (starting in the middle of a page instead of on a page boundary). Misaligned partitions cause slow read/write/reallocate performance. Instead of using Disk Management to create additional partitions, use the command-line program DISKPART and specify Align=1024 as part of the Create Partition command. See https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-vista/cc766465(v=ws.10) for the complete syntax.
- The TRIM command is not enabled for the drive: The purpose of the TRIM command is to provide a way for Windows 10 to notify an SSD of data that is no longer needed. The SSD can delete that data and the space can be made available to the machine. The freed-up space can provide for better disk performance. If the drive does not support TRIM, you must periodically run a utility provided by the drive vendor to reallocate deleted drive sectors. If the drive supports TRIM and you are using it with Windows 10, Windows needs to be optimized for use with SSDs.
- Not optimizing the operating system for use with SSDs: Although Windows 10 is designed to disable SuperFetch, defragment, and other services that can slow SSD performance, Windows does not always detect an SSD as an SSD. Use the SSD Tweaker utility (www.elpamsoft.com) to configure Windows for maximum performance with SSDs.
Tip: Instead of enabling TRIM in real time, Linux users should periodically run the command fstrim and use the Ext4 file system. For details, see https://wiki.archlinux.org/index.php/Solid_State_Drives.
Grinding and Clicking Noises
Magnetic hard disk drives are generally quiet. Loud noises coming from a drive can have at least two causes:
- A loud clicking noise is typically caused by repeated rereads of defective disk surfaces by the hard disk drive heads: This is typically a sign of a failing drive. Immediately make a backup copy and replace the hard disk.
- Humming noises can be caused by rapid head movement on a normally functioning hard disk: This noise can be reduced or eliminated by enabling Automatic Acoustic Management (AAM), a feature of most recent hard disks. Some vendors provide a downloadable acoustic management tool that can reduce head speed to reduce noise; it might reduce drive performance as a result.

Note: A softer clicking noise is typical of hard disks when the system is in sleep mode. Changing the hard disk drive’s power management settings, also known as Advanced Power Management (APM), can eliminate this noise. To learn more, see www.reddit.com/r/techsupport/comments/2zmvex/while_in_sleep_mode_laptop_hd_seems_to_make_a/.
Failure to Boot
The primary hard drive is almost always the boot drive. Failure to boot can be caused by these issues:
- The boot sequence does not specify the system hard disk, or lists the system hard disk after other drives with nonbootable media: Use the Boot Sequence dialog box in the system BIOS to configure the hard disk as either the first boot device or the second boot device, after the optical drive or USB. If a USB flash drive is listed as the first boot device and the system is started with a nonbootable USB flash drive connected, the system boot process stops and displays a boot error.
- CMOS settings have been corrupted and the system cannot find a bootable drive: Reconfigure the CMOS settings, specify the system drive as a boot drive, and restart the system. Replace the battery if the settings continue to be corrupted.
- The boot configuration data (BCD) store that Windows uses to control disk booting has been corrupted: To learn how to fix this problem, go to https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/bcdedit-command-line-options?view=windows-11.
Bootable Device Not Found
A bootable device not found issue can involve problems with cabling, power, BIOS settings, or hard disk failure. If the hard disk is running (you can usually hear faint sounds from a working hard disk), check the following:
- Bus-powered USB hard disk not recognized: A bus-powered USB 2.0 or USB 3.0/3.1 hard disk needs 500mA of power to run (and some hard disks temporarily use more power to spin up). Some computers don’t provide enough power in their root hubs (built-in USB ports) to support a bus-powered hard disk, and bus-powered hubs can provide only 100mA of power per port. Connect the drive to another port on a different root hub (each pair of USB ports is a root hub) or a self-powered USB hub, or use a Y-cable to pull power from two USB ports. Figure 5-15 illustrates a USB 3.0/3.1 Y-cable.


USB 3.0/3.1 Y-Cable Provides Bus Power from Two USB Ports
- USB or Thunderbolt drive not recognized: If the data cable between the drive and the port is loose, the drive will not be recognized. Reconnect the cable to both the drive and the port; the drive then should be recognized. If the drive is connected to a front-mounted port, make sure the port header is securely connected to the motherboard.
- SATA hard disk or SSD drive not recognized: Loose or missing power or data cables cause this problem. Shut down the computer, disconnect it from AC power, and reconnect the power and data cables. If you use Y-splitters or converters to provide power to some drives, keep in mind that these can fail. See Figure 5-16.


A Molex-to-SATA Power Converter Cable Is a Potential Point of Failure
Data Loss/Corruption
Users can experience data loss or corruption on their computer for many reasons. Many of them are due to hardware or software failure, and those are covered throughout this section. It is worth mentioning the many ways in which humans inflict damage to data through careless use of their computers and devices:
- Accidently deleting data in folders
- Unintentionally formatting a hard drive (although data can often be recovered with good backup procedures in place or with recovery tools)
- Spilling liquids on laptops or, worse, dropping devices into water
- Using poor security practices and allowing malware and viruses into the network (Ransomware takes down entire networks, not just one user!)
As a technician, you will encounter these problems (and problem users). Knowing how to respond to the damage is important. Skills you can use to solve these problems are listed here:
- Know your company’s backup systems and how to recover data.
- Keep food and drinks away from workspaces.
- Remind teleworkers that home environments have many more hazard areas than the standard office, and encourage them to keep children and pets away from equipment.
- Instill and enforce good security practices to keep hackers and viruses at bay.
As a support technician, controlling the users’ behavior is not always easy, but advocating and modeling best practices are always important.
RAID Failure
RAID failure problems can result from the following:
- The RAID function is disabled in the system BIOS: Reconfigure the BIOS to enable RAID on the SATA ports used for RAID, and restart the system.
- Power or data cables to RAID drives are disconnected: Reconnect the cables to the RAID drive(s) and restart the system.

Note: Some motherboards offer RAID support from the chipset, as well as a separate RAID controller chip. Be sure to identify which SATA ports are controlled by the chipset versus a separate RAID controller chip, and connect the drives accordingly.
A RAID failure might be caused by the failure of one or more of the disk drives in the RAID array. Take the following steps if a single drive failure occurs:
- RAID 0: Determine which drive has failed. Replace it and follow the vendor’s recommendations to re-create the array. Restore the latest backup. Any data that has not been backed up is lost.
- RAID 1, RAID 10, and RAID 5: Determine which drive has failed. Replace it. Follow the procedures provided by the RAID vendor to rebuild the array.
If both drives have failed in a RAID 0 or RAID 1 array, you must rebuild the array with new drives and restore the latest backup. Any data that has not been backed up is lost.
If two or more drives have failed in a RAID 10 or RAID 5 array, your recovery options might vary according to the exact configuration of the array. See the RAID vendor’s procedures for details and recovery options.
S.M.A.R.T. Failure
Both Serial ATA (SATA) hard disks and older Parallel ATA (PATA or ATA/IDE) hard disks support a detect-warning feature known as Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T.—also referred to as SMART). S.M.A.R.T. monitors internal hard disks and warns of impending failure. Typical items monitored include the following:
- Drive temperature
- Read retries
- Slow spinup
- Too many bad sectors
Typical S.M.A.R.T. warnings include these:
- Hard disk failure is imminent
- A hard drive in your system reports that it may fail
- Smart failure imminent, back up your data
When S.M.A.R.T. errors appear, back up the system immediately. To determine whether the drive is actually bad or whether the message was a false positive, download and run the disk testing software provided by your system or drive vendor. The long or complete tests detect surface problems and might also swap defective sectors for good sectors.
Under normal operating conditions, you should test your hard disks every month by using a program such as chkdsk (included in Windows) or a vendor-supplied hard disk utility, and review the S.M.A.R.T. attributes for errors. On a portable or laptop hard disk, I recommend checking twice a month because these drives are in greater danger of being physically damaged or overheating.
Although third-party S.M.A.R.T. attribute testing apps are available from many sources, drive manufacturers recommend using their own apps because they are more reliable in interpreting test results and warning of immediate problems.
Extended Read/Write Times
Hard drives should perform at about the same speed throughout their lifetime. If status LEDs indicate longer read/write times, consider checking for a few common culprits:
- Run a virus scan.
- Check the Task Manager to see which programs are using the most resources. Close unused programs.
- Check the Task Manager’s Startup tab and uncheck any unnecessary startup programs to reduce the load running in the background.
- Check for drive errors. In Windows 10, open File Explorer and right-click the drive that is slow. Then select Properties and open the Tools tab. Use the Check and Optimize utilities to free up space.
- The problem could be with the SATA cable or its connection to the port. Reconnecting (or changing) the SATA cable or using a different SATA port might be all it takes to fix the issue.

Input/Output Operations per Second (IOPS)
Input/output operations per second (IOPS) is the standard way to measure the performance of hard disk drives (HDDs) and solid-state drives (SSDs) in a computer. The IOPS number is a measure of the speed at which data can be read and written from the drive to the CPU.
Remember that HDDs are mechanical and the rotating platters limit the speeds of various HDDs. HDD IOPS run at a relatively slow speed, in the range of 150 to 250 IOPS; current SSDs are delivering around 620,000 IOPS. The performance difference between the types of storage drives explains why migrating to an SSD can greatly enhance the user’s experience.
It is possible to collect and monitor the IOPS performance in Windows 10 using the Performance Monitor by typing perfmon in the Windows 10 search area, opening the Resource Monitor, and selecting Disk. These new tools allow a deep dive into the drive’s performance.

Missing Drives in OS
An “OS not found” (or “operating system not found”) error during boot can be caused by these drive errors:
- Nonbootable disk in the USB drive: If a USB drive is listed before the hard disk in the boot sequence and it contains a nonbootable disk, the computer displays an error message that it cannot find the operating system. Remove the USB flash drive and restart.
- Boot sequence not listing the hard disk: Restart the computer, start the BIOS/UEFI setup procedure, and make sure that the hard disk is both listed as a bootable drive and listed before options (such as network boot).
- Incorrect installation of another operating system: Windows automatically sets up its own boot manager for access to more than one Windows version if you install the older version of Windows first, followed by the later version. However, if you install a newer version first and then later install either an older version or a non-Windows OS, you cannot access the newer Windows version unless you install a custom boot manager.

Note: For more information about solving boot problems that involve operating system issues, see Chapter 6, “Operating Systems.”
Occasionally, a Windows 10 update or reconfiguration resets the presentation of the disk drives in the OS File Explorer and other areas. The drive might be there one minute, and then after an event (a reboot, an update configuration, or some other event), a drive letter disappears. Fortunately, in many cases, the drive is still present; it is just not scanned as a drive and presented as a drive icon.
First, check the physical connections. The cables might appear to be connected properly, but reseating them (or changing the cable) is always a good first step. Try to eliminate easy physical problems before diving into more complex troubleshooting.
The easy way to ensure that the drive is still there is to right-click the Start button and select Disk Management from the menu. If the drive is there but is missing a name, the following steps should repair it. Figure 5-17 captures this moment when the D drive was “missing.” The problem was resolved in the Disk Management window by right-clicking Disk 1, selecting Change Drive Letter and Path, then selecting Change, and finally simply assigning a letter from the drop-down menu.


Steps for Assigning a Missing Drive Letter
The problem also can be repaired by simply rescanning the drive from Disk Management.