Why ‘Bit Rot’ is destroying your data
Cloud storage can be expensive, so an alternative for many people is to simply grab all the important memories and store them on a hard drive to revisit them later.
Unfortunately, this is a bad idea and if you do this you’ll probably want to spin this disk up as soon as possible. Enter the concept of Bit Rot: the silent killer for your precious photos and videos and, frankly, any files you might have on that old, dust-filled drive.
What’s a little rot?
At its most fundamental level, bit rot, formerly known as data decay or data decay, is what we call the progressive degradation of storage media and the subsequent corruption of the information residing on it. Remember that even though technology has advanced, data still exists and is stored as binary code, made up of zeros and ones. The way a hard drive works is that these bits are recorded by magnetizing tiny microscopic sectors on a rotating platter. A north pole can represent a one, while a south pole represents a zero.
Over time, these magnetic domains can lose their orientation due to the natural tendency of magnetic polarity to disperse, a process often accelerated by environmental factors. When a bit flips (from zero to one or vice versa) without the operating system explicitly commanding this change, bit rot has occurred. And a small turnaround can have catastrophic consequences.
This is quite dangerous because it is a silent process. Unlike a catastrophic drive failure where the mechanical arm breaks or the motor burns out, bit rot occurs at the molecular level. It’s physics. The file system may still show the file as existing, occupying the correct amount of space and retaining its original creation date. However, the internal structure of the file has fundamentally changed, all because of this change. If the rot affects a non-critical part of a text file, you might just see a random character appear in a sentence. However, if this inverted bit resides in the header of a photo file or the keyframe of a video, the entire file may become unreadable. The computer attempts to open the image, encounters code that no longer makes sense, and simply displays an error message or a corrupt, pixelated mess. It’s the digital equivalent of ink fading on a page until the words are no longer legible, which happens without your knowledge until you try to access the memory years later.
Is this common?
The prevalence of bit rot is widely misunderstood as it is often confused with total hardware failure, but it is an almost inevitable event given a long enough delay. The question is not whether a storage medium will degrade, but rather when.
In the context of magnetic hard drives, which are the most common medium for long-term storage of old photos, the magnetic signature required to retain the data is not permanent. While modern error correction code (ECC) built into hard drives is designed to detect and correct these minor errors as they occur, this defense mechanism requires the drive to be powered on and reading data. When a drive sits in a drawer, unplugged from the power supply for years, error correction systems remain inactive, allowing progressive magnetic degradation to build up unchecked. This is why this happens to old drives that have been unplugged after years of disuse, and not to drives that work all the time.
The frequency of this degradation is highly dependent on the quality of the disk and the environment in which it is stored. High heat and humidity are the main accelerators of bit rot. In a hot attic or damp basement, chemical degradation of the disk’s protective layers and thermal agitation of magnetic particles significantly accelerates data loss.
This is not exclusive to spinning hard drives. SSDs, which store data using electrical charges in floating gate transistors, might actually be even more prone to data loss when not powered. The electrical charge leaks over time, causing data corruption much faster than the magnetic degradation of traditional drives.
Although cosmic rays and background radiation can statistically cause bit flips, the most common culprit is simply the entropy of physical materials. Every hard drive currently sitting in a closet slowly undergoes this process.
Should I be worried about this?
If your goal is to preserve a digital family album for decades, bit rot is absolutely a cause for concern, especially because of the passive way most people treat archive storage. The “set it and forget it” mentality is the biggest risk factor for digital photos. Many users treat hard drives like time capsules, burying them in a box in the hopes of unearthing them twenty years later to find them intact. Please don’t do this. Digital storage media are not archived in the same way as acid-free paper or stone tablets. This requires active maintenance.
If you’re using a single external hard drive that hasn’t been plugged in since 2015, there’s a statistically significant chance that some of those files have already been corrupted.
There is no such thing as a “perfect” hard drive that is not prone to rot, so what are your solutions for archiving? It is wise to keep several copies on different types of media and check them periodically. This is often called data cleansing, where files are read and checked against checksums to ensure their integrity.
If you don’t want to do this, or can’t, simply turning on their archive drives once or twice a year and making sure the files open correctly can allow the drive’s firmware to refresh the data. Don’t leave it unplugged for years and expect everything to be fine.
