How to Tell If Your Hard Drive Is Failing

The noises that mean stop right now

A traditional hard drive is a stack of spinning platters with a head that floats a fraction of a hair's width above the surface. When you hear a rhythmic click — often described as a click of death — that head is failing to find its position and resetting, over and over. Every one of those cycles risks the head touching the platter and scraping the magnetic layer off the surface. Once that layer is gone, the data that was on it is gone with it, and no software and no lab can bring it back.

The same goes for grinding, scraping, or a high-pitched whine that changes pitch. These are physical sounds from a physical problem, and the correct response is to shut the machine down and leave it off.

What people usually do instead is keep rebooting to see if it comes back, or run a disk repair utility. Both make it worse. Repair utilities write to the drive, and writing to a physically failing drive both consumes its remaining healthy life and can overwrite the very structures a recovery would use to rebuild your files.

If a drive is making noise, the cheapest thing you will ever do is turn it off and bring it in. I have recovered full drives that arrived quiet after one bad night, and recovered almost nothing from drives that ran for another week.

The symptoms that mean back up today

Not every warning is audible. These are the ones I see most often on the bench, and they are the stage at which recovery is still cheap and usually complete.

• Files that disappear or won't openA document that was there last week and is gone now, or a photo that opens as garbage, usually means the drive's own sector map is developing holes. The file isn't corrupted by an app — the storage under it is failing.
• Long freezes with no CPU loadThe machine locks for 10–30 seconds, then continues as if nothing happened. That pause is the drive retrying a bad sector until it gives up. If the fans stay quiet during the freeze, it's the drive, not the processor.
• Boot time going from seconds to minutesGradual slowdown over a year is usually software. A machine that booted in 30 seconds last month and takes four minutes today is not a software problem.
• S.M.A.R.T. warnings at startupThe drive's own firmware has decided it is failing. This is the one warning people most often click past. Treat it as final — the drive is telling you it has already used up its spare sectors.
• Repeated 'repairing disk errors' on WindowsOnce is a bad shutdown. Every boot means the filesystem is being damaged faster than it can be fixed, and the cause is underneath the filesystem.

SSDs fail differently, and more suddenly

Almost all the advice online is about spinning drives, because that is what people wrote about for twenty years. Solid-state drives have no moving parts, so they give you no audible warning at all — which makes them more reliable right up until they are not.

The typical SSD failure I see is one of two things. Either the drive flips into a read-only state, where everything is still there but nothing can be written, or the controller dies and the drive simply stops appearing in the BIOS as though it were unplugged. The read-only case is good news: your files are intact and copying them off is straightforward. The controller case is much harder, because the data is still on the flash chips but the part that knows how to read them is dead.

The practical consequence is that with an SSD you get less warning, so backups matter more, not less. A drive with no moving parts is not a drive that cannot fail.

What it costs to act early versus late

The gap between the first and last row of that table is usually a matter of days, and it is almost entirely under your control. That is the whole reason this page exists — the single highest-value thing I can tell anyone about storage is that the cheap version of this problem and the expensive version are the same problem caught at different times.

What to do in the next ten minutes

• If you hear noise: power off nowHold the power button. Do not restart to check. Do not run chkdsk, Disk Utility, or any recovery software.
• If it's quiet but symptomatic: copy your irreplaceable files firstPhotos, documents, tax records. Not the whole drive — the things you cannot get back. Copy them to an external drive or cloud storage before anything else, because a full clone puts hours of extra load on a drive that may not have hours left.
• Don't defragmentDefragmenting rewrites large portions of the drive. On a healthy drive that's harmless. On a failing one it is close to the worst thing you can do.
• Bring the whole machine if you canIt saves guessing about how the drive was configured, and lets me test whether the controller or cable is the actual fault rather than the drive itself. That happens more often than people expect.