What are the warning signs that a hard drive is about to fail?
The signs arrive in a rough order, and the window for getting data off narrows as you go. Which symptoms mean act now, and which mean act today.
- Difficulty
- beginner
- Time
- 30 min
- Read
- 4 min
- Safety
- warning
Short answer
Earliest and most useful: a rising reallocated-sector count in the drive's own health data, with no symptoms at all. Then intermittent slowness, files that take an age to open, and applications freezing. Then read errors, files that will not open, folders that vanish, and the machine failing to start. Finally clicking, grinding or the drive not being detected — by which point you are into professional recovery. Copy your data off at the first sign, not the last.
Mechanical drives usually decline gradually and give warnings, which is why the health data is worth checking occasionally. Solid state drives usually do not: they work, then abruptly do not. That difference should change how you treat each.
Safety
Step by step
- Read the drive's own health data.Every drive keeps self-monitoring statistics. Free tools on Windows and macOS display them. Three figures matter: reallocated sector count, pending sector count and uncorrectable sector count. All should be zero. Any of them rising over weeks means the drive is consuming its spare capacity and is on its way out.
- Treat a rising count as a decision, not an emergency.A drive with a handful of reallocated sectors will often run for months. It will also sometimes fail next week. Copy everything off now while it is easy, then plan a replacement at your convenience.
- Notice the performance symptoms.A machine that freezes for ten seconds while opening a folder, copies that crawl and then recover, the fans running while nothing appears to happen: these are the drive re-reading sectors repeatedly to get a good result. It is a genuine and often-missed signal.
- Take file-level errors seriously.A photo that will not open, a document that reports corruption, a folder that appears empty and then does not. If these are appearing across different files and different applications, the fault is the drive, not the files.
- Act at the first noise.Clicking, a repeated seek-and-reset sound, grinding, or a drive that spins up and down. Power it off. Not later — now. This is the end stage and every further minute of operation reduces what a laboratory could retrieve.
- Copy the important things first.Do not start a full image of a failing drive with your photographs at the end of it. Copy the irreplaceable material first, then the useful, then take an image if the drive is still alive. Priority order is the whole strategy on a dying drive.
- Recognise how SSDs fail instead.Solid state drives report wear as a percentage of endurance used, which is worth checking but rarely the cause of failure. They more often fail by the controller dying with no warning, or by the drive dropping into a permanently read-only state. Read-only is a gift: copy everything off immediately and replace it.
- Replace on age as well as on symptoms.A drive in daily use past about five years is on borrowed time whatever the health data says, and a backup drive of that age should be retired. Drives are cheap relative to the data.
If it doesn't work
Computer freezes for seconds at a time, then recovers
Cause: The drive is retrying bad sectors — Fix: Check the health data. If sectors are being reallocated, copy the data off and replace the drive. If the drive is clean, look at memory, an overheating processor or a background process instead.
Machine will not start and reports no boot device
Cause: System drive failing or the file system damaged — Fix: Do not reinstall. Take the drive out, connect it to another machine as a secondary drive, and copy off what you can. Reinstalling first is a common and expensive mistake.
External drive disconnects and reconnects
Cause: Often the cable, port or power supply rather than the drive — Fix: Change cable and port first, and use a powered connection for a desktop drive. If it persists across cables and machines, suspect the drive.
Health data shows a warning but everything works fine
Cause: Reallocated sectors, drive still functioning on spares — Fix: It is a real warning. Copy off, order a replacement, and stop using it for anything that matters. It is not an emergency today.
SSD has become read-only
Cause: The drive has entered a protective mode at end of life or after a controller fault — Fix: Copy everything off immediately while you still can, and replace it. This state does not reverse and can be followed by the drive disappearing entirely.
Keeping on top of it
- Check drive health statistics on every computer (Twice a year)
- Verify the backup and note the date on the drive (Every six months)
- Retire drives in constant use (At about five years)
- Check external backup drives spin up and read correctly (At each backup)
Questions people ask
Can a failing drive be repaired?
Bad sectors can be marked so the system stops using them, which keeps a drive limping. It does not fix the underlying degradation and the count will keep rising. Treat it as a way to buy time for the copy, not a repair.
Does the operating system warn me?
Both Windows and macOS will warn on a clear failure prediction, and both miss slow degradation. The warning is worth acting on immediately; its absence is not reassurance.
Is a noisy drive always failing?
No — normal seek chatter and spin-up are audible on many mechanical drives. What matters is a change: a new rhythmic click, a repeated cycle of spin-up and stop, or grinding.
Should I run a full surface scan to check?
On a drive you suspect, no — not until the data is copied off. A full scan reads every sector and is exactly the stress that finishes a marginal drive.