How does a hard drive get corrupted?

What is a Hard Drive?

A hard disk drive (HDD) is the primary data storage device used in computers (Crucial). An HDD is a non-volatile storage device, meaning it retains data even when powered off (TechTarget). The main components of a hard drive include:

  • Platters – circular disks that store data magnetically
  • Read/write heads – devices that read and write data to the platters
  • Spindle – rotates the platters at high speeds
  • Actuator arm – moves the read/write heads across the platters

Data is stored on the platters in concentric tracks. As the platters spin at speeds up to 15,000 RPM, the read/write heads float just above the surface on an air bearing and rapidly access data (Wikipedia). The heads can locate specific data by moving across the arm to different tracks and sectors. This allows a hard drive to store and retrieve data very quickly.

Causes of Hard Drive Corruption

There are several common causes that can lead to hard drive corruption:

  • Bad sectors – Areas on a hard drive’s magnetic platter surface that can no longer reliably store data due to damage or manufacturing defects. This damage prevents the drive from being able to read or write data in these sectors, leading to data loss or corruption. Bad sectors often increase as a hard drive ages.
  • Firmware bugs – Bugs or errors in a hard drive’s firmware code can lead to corruption or catastrophic failure. Firmware controls all the operations and functions of a drive. Bugs may occur due to coding mistakes or faulty updates.
  • Power outages – An sudden power loss while the drive is writing data can corrupt files and the file system. The heads may fail to retract properly leading to physical damage.
  • File system errors – The file system manages how data is stored on the drive. If it becomes corrupted, data may become inaccessible or corrupted. Common causes include sudden power loss, improperly disconnected drives, or file system bugs.

Damage or corruption in critical areas like the partition table, master boot record, or file system metadata can render all data on the drive inaccessible. Electrical surges, power spikes, and long power failures also commonly lead to corruption.

According to My Data Recovery Lab, physical damage from drops or shocks, overheating, firmware bugs, file system errors, and malware/viruses rank among the most prevalent causes of hard drive failure and data loss.

Bad Sectors

A bad sector is a tiny cluster of storage space on a hard drive that appears defective or damaged, making it inaccessible or unreadable by the drive (Howtogeek, 2013). When a sector becomes damaged, any data stored in that location is lost. Bad sectors most commonly develop due to physical damage or manufacturing defects.

Bad sectors can occur when the magnetic coating on the hard drive platter becomes damaged or corrupted. This can happen gradually over time through normal wear and tear. It may also occur suddenly as the result of a physical jolt or shock to the drive. Bad sectors may also be present from the start as a result of an imperfection or contaminant on the platter surface during manufacturing (Wikipedia, n.d.).

The main symptom of bad sectors is data corruption, freezing, or general performance issues. The drive will have difficulty reading data in areas marked as bad sectors. You may experience crashes, lag, or the inability to access files. Lost clusters of data can appear as glitches or pixelation in photos, videos, and other media.

Firmware Bugs

Firmware is the code programmed on the hard drive’s controller chip that tells it how to operate. Like any software, firmware can contain bugs or errors that prevent the drive from working properly (Source). Firmware bugs can occur if the code wasn’t properly tested or updated. Bugs may only affect certain drive models or batches.

Firmware bugs can manifest in different ways. Some bugs may cause intermittent freezing, crashing, or failure to boot. Others can lead to slow performance, corruption of data, or the drive not being detected. Often firmware bugs surface after a drive update, but some exist from the start. The effects range from minor glitches to complete drive failure.

While firmware bugs can be difficult to diagnose, warning signs include drives freezing during the boot-up sequence or specific operations repeatedly causing hangs or crashes. Updating to the latest firmware version can fix bugs, though a firmware rollback may be required if the new version contains bugs itself. For severe corruption, low-level drive repair or data recovery services may be necessary to access the contents (Source).

Power Outages

A sudden loss of power or electrical spike can corrupt data on a hard drive by interrupting write operations or damaging electronic components. When power is cut during a write operation, the OS can’t save all the data to disk, leading to file corruption or data loss. Power surges can short circuit components like the hard drive’s controller board, motors, or read/write heads. This physical damage often makes data recovery difficult or impossible (

To reduce the risk of corruption from power outages, use an uninterruptible power supply (UPS) to provide backup power and protect against surges. Set your computer to hibernate instead of sleep, so it can save data and safely power down during an outage. Consider cloud backups or a NAS with battery backup to recover lost files. Avoid accessing the hard drive immediately after an outage, as components may be unstable. Overall, modern drives are resilient to brief power loss, but extreme electrical events can still cause irreversible damage (

File System Errors

The file system structure refers to how data is organized and stored on a hard drive. It controls how files and folders are named, where they are placed, and how the storage space is allocated. The two most common file systems for Windows are NTFS and FAT32.

File system errors occur when the structure of the file system gets corrupted. This can happen due to various reasons like bad sectors, power outages, drive failure, etc. Common file system errors include:

  • File system corruption – The structure of the file system is damaged and needs to be repaired. This can cause data loss and prevent accessing files.
  • File system fragmentation – Files get scattered across the drive over time leading to reduced performance. Defragmentation is required to reorder and optimize file storage.
  • Invalid file names – File names contain invalid characters that the file system cannot recognize.
  • Cross-linked files – Two files point to the same data clusters causing data inconsistencies.

advanced recovery software is often required to fix file system errors. Preventative measures like disk maintenance, data backups, and surge protection can help avoid file system damage.

Accidental Deletion

Accidentally deleting files is one of the most common ways hard drive corruption occurs. When a file is deleted from a hard drive, the file itself is not actually removed from the disk. Instead, the file system marks the space occupied by the deleted file as being available for new data. The original data from the deleted file remains on the disk until it is overwritten by new data.

If critical system files are accidentally deleted, it can prevent the operating system from functioning properly. The computer may fail to boot or operate correctly. Likewise, accidentally deleting important personal files like documents, photos, or other data leads to data loss and corruption from the user’s perspective.

There are methods to recover accidentally deleted files if they have not already been overwritten. As recommended by EaseUS and SalvageData, recovery software can scan the hard drive and restore deleted files. However, the sooner data recovery is attempted after accidental deletion, the higher the chances of recovering the lost data before it is overwritten. Preventative measures like backups are recommended to avoid permanent data loss.

Malware and Viruses

Malware like viruses, worms, and Trojan horses can infect and damage files on a hard drive, causing corruption or even complete failure. Viruses like the boot sector virus can overwrite key boot files, preventing the computer from starting up properly. File-infecting viruses can modify and corrupt data files stored on the hard drive. Some viruses are designed to intentionally overwrite or erase files as part of their payload. Malware can also exploit security vulnerabilities to gain access to protected system files and settings, which can lead to instability and crashes.

Viruses spread through infected programs, files, email attachments, and infected external drives. Practicing safe computing by not opening suspicious emails/files, using antivirus software, and being cautious when plugging in external drives can help prevent malware infection leading to hard drive corruption.

Specific malware threats like the FAT virus can damage or overwrite the file allocation table, preventing access to data stored on the hard drive. The only way to remove these viruses is through a thorough scan and cleaning using antivirus tools. If the damage is severe, a full reformat and OS reinstall may be required. Backing up data regularly provides protection in case malware results in catastrophic drive failure.

Physical Damage

Physical damage to a hard drive is one of the most common causes of corruption and data loss. This type of damage occurs when the physical components of the drive are impacted in some way. For example, dropping an external hard drive can cause the read/write heads to hit or scrape the platters, resulting in scratched surfaces or misaligned parts.

According to an article on LinkedIn, physical damage like a drop impact can make data recovery extremely difficult if not impossible in some cases: “Physical damage is damage to the hard drive’s hardware, such as the platters, heads, or motor. This can be caused by dropping the drive, which can make the heads crash into the platters and cause irreparable damage.” (Source)

Even a small amount of physical damage to the platters can result in corrupted or unreadable sectors. Once sectors become corrupted or unable to be read, the data stored in them is often irrecoverable. As noted on SuperUser, “A huge hard drive with data that has one bad sector would be practically impossible recover. I highly doubt anything would be read.” (Source)

Other forms of physical damage include hardware component failures. For example, the motor breaking or the read/write heads malfunctioning. Any disruption to the intricate mechanical parts inside a hard drive puts data at risk.

Preventing Corruption

There are several steps you can take to help prevent hard drive corruption from occurring:

  • Perform regular backups of your data to an external hard drive or cloud storage. Backing up data ensures you have copies in case the original data becomes corrupted or lost. Some recommend backing up daily for critical files.
  • Use a surge protector. Power surges and sudden power disruptions can damage hard drives. Using a surge protector or battery backup unit can regulate power and prevent damage.
  • Scan your hard drives for errors. Use built-in hard drive utilities like CHKDSK in Windows or Disk Utility on Mac to scan for and repair errors.
  • Keep your hard drives cool and well ventilated. Overheating can lead to corruption. Make sure it is not in an enclosed space and the vents are clear.

While you cannot completely guarantee a hard drive will never become corrupted, following precautions like routine backups, power regulation, and disk monitoring can greatly reduce the chances of corruption occurring.