Hard drives store data magnetically on platters inside the drive enclosure. Data corruption refers to errors or damage to the data stored on the drive, making it inaccessible or unusable. There are several common causes of hard drive corruption:
Sudden loss of power can cause the drive heads to crash onto the platters, physically damaging them. Connectivity issues like bad cables can cause data transfer problems and corruption. Viruses and malware can intentionally overwrite or encrypt data. File system errors can make data unreadable by the operating system. Bad sectors are areas of physical damage on the platters.
Many people assume unused hard drives are safe from corruption over time. However, there are factors that can still lead to data loss and corruption on drives that are powered off and disconnected. We’ll explore some of these potential causes.
In this article, we’ll dive deeper into how hard drives store data, what causes corruption, steps to prevent it, how to check for and recover corrupted data, alternatives for storing unused drives, and more.
How Hard Drives Store Data
Hard drives store data magnetically on rapidly spinning circular platters made of glass or aluminum. These platters are coated with a thin magnetic film consisting of tiny magnetized particles. The platters are stacked on top of a spindle and spin at very high speeds, typically 5400 to 15000 RPM.
Data is written and read by a head actuator arm that has read/write heads on the end. The read/write heads float very close above the surface of the platters on a cushion of air. They do not physically touch the platter surface. As the platters spin, the heads can access different areas of the platter to read or write data. There can be multiple platters stacked, each with two read/write heads, allowing large amounts of data storage.
To write data, an electrical current is sent to the read/write heads to orient the magnetic particles on the platter into patterns of 1s and 0s. These magnetized patterns represent the data. To read data, the heads detect the magnetized patterns and convert it back into 1s and 0s.
According to Stanford University (https://cs.stanford.edu/people/nick/how-hard-drive-works/), modern hard drives can store over a trillion bits of data per platter due to the tiny size of the magnetic particles. This allows for immense data storage capacity.
Common Causes of Corruption
According to Salvagedata, there are a few common causes that can lead to hard drive corruption and failure [1]:
Physical Damage: Physical damage from drops, impacts, or scratches can damage the platters or internal components of a hard drive. This physical trauma can lead to irreparable corruption.
Overheating: Excessive heat can cause hardware malfunctions, firmware bugs, or magnet/platter degradation. Ensuring proper ventilation and airflow is key to preventing overheating issues.
Firmware Bugs: Firmware is embedded software in the hard drive controlling read/write functions. Bugs here can catastrophically disrupt drive behavior. Firmware updates aim to patch bugs and improve stability.
Power Outages: Abrupt loss of power during a drive operation can corrupt file systems and crash the drive. Using an uninterruptible power supply minimizes power disruption risks.
Corrosion Over Time
Hard drives contain platters coated with a thin magnetic film that is used to store data. When a hard drive is not powered on and in use, the platters remain stationary inside the drive enclosure. Over time, even in normal conditions, the platters can start to corrode as oxygen interacts with the magnetic coating. According to an answer on Super User, the magnetic platters can start to degrade in as little as 5 years when left unused and unpowered.
One of the main concerns with corrosion on the platters is that the oxide layer will begin to break down. As the magnetic coating corrodes, data stored on the drive can become unreadable. An unused hard drive provides the perfect environment for corrosion to occur steadily on the platter surface. Without the motion of the spinning platter and read/write heads, corrosion has time to build up through oxidation.
Hard drive platters are also susceptible to physical damage from corrosion. If moisture were to enter the drive enclosure somehow, then rusting could occur on internal components. As pointed out on the Forensic Focus forums, rust could lead to the drive seizing up or malfunctioning. So while the platters themselves are generally resistant to water damage, rust on other parts could still affect the drive’s functionality.
Degradation of Magnets
Magnets lose strength over time due to a process called magnetic relaxation. The individual magnetic dipoles within a magnet tend to become randomly oriented over time due to thermal fluctuations, which causes the magnetization to decrease (https://www.newscientist.com/lastword/mg24732911-800-does-magnetism-decay-over-time/). Permanent magnets are estimated to lose around 1% of their magnetic field strength per year, though the rate depends on the material and temperature (https://www.reddit.com/r/DataHoarder/comments/lll1gq/do_hdds_actually_decay_and_lose_data_if_sitting/).
Since hard drives store data using magnetic patterns on the platters, degradation of the magnets over time can impact stored data. As the magnetic field strength decreases, the integrity of the data patterns also diminishes. This can eventually lead to data corruption or loss of data if the magnetic flux density drops below the level needed for the read/write heads to detect the bit patterns. However, under normal storage conditions, magnetic relaxation occurs slowly enough that data loss is unlikely over the typical lifetime of a hard drive.
Preventing Corruption
The best way to prevent corruption on unused hard drives is to store them properly and spin them up occasionally. Hard drives should be kept in a cool, dry place inside anti-static bags, and can be placed in plastic storage containers for extra protection. Using anti-static bags prevents any static buildup from damaging the drive’s components. Storing drives in a climate-controlled environment also helps prevent corrosion over time.
It is also important to spin up unused drives every 6-12 months. Powering on the drive briefly allows the platters to spin and the head to check for any issues. This prevents the components from getting stuck in place and helps maintain proper mechanical function. Occasional spin-ups make sure the drive stays in working order in case you need to access the data down the road.
Proper storage and occasional usage are simple but vital steps to prevent file corruption on unused hard drives. Following best practices will keep drives functional and ready for use when needed.
Checking for Corruption
There are a few key signs that a hard drive may be corrupted, even if it hasn’t been used in a while. These include the drive not being recognized by the computer, frequent crashes and freezes, strange noises coming from the drive, and problems opening files stored on the drive 1. Corrupted drives may display errors like “Sector not found” or report a much smaller capacity than advertised.
To scan for and attempt to repair corruption, the CHKDSK utility is built into Windows and can analyze the file system integrity of drives 2. Running CHKDSK will scan for bad sectors, lost clusters, cross-linked files, and directory errors. It can then recover readable data if possible. To use CHKDSK, hit Start, type “cmd” to open the command prompt as admin, type “chkdsk C: /f” and hit Enter to scan C drive. chkdsk can take a while to run but is a handy built-in tool.
Third party disk utility software like Spinrite or Disk Drill can also run more comprehensive scans to identify and repair corruption across the entire drive. But if corruption is severe, a full backup and reformatting the drive may be necessary.
Recovering Corrupted Data
If hard drive corruption occurs, there are ways to recover the data. The most effective methods involve using data recovery software or sending the drive to a professional data recovery service.
Data recovery software like EaseUS Data Recovery can scan the corrupted drive and extract recoverable data. Software looks for intact sectors of the drive that still store data. This allows recovering documents, photos, videos, and other file types. Software options provide an affordable solution for DIY data recovery.
For more severe corruption that software cannot handle, professional data recovery services may be able to recover the data. Services like DriveSavers have advanced tools and clean room facilities to repair drives and extract data. While costly, these services offer the best chance for recovering data from a severely corrupted drive. They can recover data after floods, fires, malware, and other major damage. Professional recovery is recommended when software cannot recover the needed data.
Storing data on unused hard drives can be risky due to potential degradation and corruption over time. However, there are safer alternatives for unused data that reduce the likelihood of data loss.
Alternatives to Unused Drives
Rather than leaving data unused on an internal or external hard drive, there are more reliable options to ensure the data remains intact.
One popular alternative is to utilize online or cloud-based storage instead. Services like Dropbox, Google Drive, Microsoft OneDrive and Apple iCloud allow users to upload files that can be accessed from any device. Cloud storage providers invest heavily in data redundancy across multiple geographic regions, making it far less susceptible to data loss. According to a study by BackBlaze, cloud storage providers average over 99.999999999% durability per year.1
For those wanting to retain local storage, external hard drives that are powered on and accessed periodically can avoid some of the magnetization and mechanical issues that impact unused drives. The key is to avoid letting drives sit powered off for extended periods of time. Refreshing the data every few months can identify potential early issues. External drives kept in a fireproof safe or safety deposit box can also provide protection if disaster strikes the primary location.
Conclusion
To conclude, hard drives that are left unused and disconnected for extended periods of time can be susceptible to corruption. Though the likelihood of corruption occurring spontaneously on an unused drive is relatively low, degradation over time of the physical components can lead to compromised data.
To prevent potential corruption, the best course of action for any unused drive is to connect it periodically, such as every 6 months or so. Simply plugging it in and accessing the files will allow the drive to run its internal checks and refresh the data. For even better protection, consider making periodic backups of unused drives to guard against physical failure.
If you do happen to find an old, unused drive and discover corruption, don’t panic. In many cases the corruption is limited and you can successfully recover meaningful portions of data. Be sure to try data recovery software and services when possible before considering the data a total loss.
