Check for Bad Sectors with DiskGenius

What a bad sector actually is

A sector is the smallest addressable block on a drive. When one can no longer hold data reliably it is a bad sector, and there are two kinds worth telling apart.

• Logical — the data in the sector is inconsistent but the medium is fine. Often fixable by rewriting the sector, and commonly caused by an unexpected shutdown.
• Physical — the medium itself is damaged. Nothing repairs it; the drive can only mark it unusable and substitute a spare.

A handful of reallocated sectors on an older drive is not an emergency. A count that keeps climbing week by week is the drive telling you its plans.

Read SMART data first

SMART is the drive's own record of its life. Open the health function, select the disk, and look at a few attributes rather than the overall verdict:

• Reallocated sector count — sectors already retired. Rising values are the clearest warning sign.
• Current pending sector count — sectors under suspicion, waiting to be reallocated. Non-zero deserves attention.
• Uncorrectable sector count — errors the drive could not fix. Back up now.
• Power-on hours — context. A drive with 60,000 hours behaving oddly is simply old.
• For SSDs, wear levelling and remaining life indicators matter more than sector counts.

Run the surface scan

1. Select the disk and open the bad track or surface verification function.
2. Start a read-only scan first. It reads every block and colours the map by response time — fast, slow, or unreadable.
3. Let it complete without using the drive for anything else, which would skew the timings.
4. Read the map: a few slow blocks are common; clusters of damage, especially spreading regions, mean the drive is deteriorating.

Never run a repair pass on a drive holding data you have not copied off yet. Repair writes to the disk, and on a failing drive writing is the last thing you want.

What to do with the results

Clean scan, healthy SMART

The drive is not your problem. Look at the file system, the cables, drivers or the application instead.

A few isolated errors, stable SMART

Make sure backups are current and rescan in a month. Note the numbers so you can see whether they move.

Growing errors or pending sectors

Copy your data off now, before anything else. Then plan a replacement. Repair attempts on a degrading drive buy time at best.

Widespread unreadable areas

Stop scanning. Repeated passes stress a dying drive. If the data matters, image the disk and work on the image, or send it to a recovery lab.

Habits worth having

Check SMART on every drive you buy, especially second hand. Rescan the drives in your machine a couple of times a year and write the numbers down. Trends tell you far more than any single reading, and a drive that warns you a month in advance is a drive you never lose data to.

Symptoms that justify a scan

• File copies that start fast and then stall at a particular file every time.
• Explorer freezing when a specific folder is opened.
• Windows taking much longer to boot than it used to, with no software explanation.
• Applications reporting that files are corrupt when they were fine last week.
• Clicking, grinding or repeated spin-up noises from a mechanical drive.
• The system logging disk errors, or a drive dropping out and reappearing.

The last two are different from the rest. Noise and disconnections are hardware talking, and the correct response is to copy data off immediately rather than to run more diagnostics.

SSD health is a different measurement

A surface scan is a mechanical drive's test. On an SSD it still finds unreadable blocks, but the more meaningful figures are wear-related: total data written, remaining endurance and the count of reserve blocks already used. A consumer SSD in a home PC usually reaches obsolescence long before it reaches its write limit, so a healthy wear figure after five years is normal rather than suspicious.

Watch instead for sudden changes — a drive that reports a jump in uncorrectable errors, or one that starts reading unusually slowly across the whole surface. SSDs tend to fail more abruptly than hard drives, which makes current backups matter more, not less.

Building a habit instead of reacting

1. Check SMART on every drive when you install it, and again on any second-hand drive before you trust data to it.
2. Rescan the drives in daily-use machines twice a year and record the key counts.
3. Compare against the previous reading rather than against an abstract idea of good.
4. Replace on a trend, not on a single alarming number.
5. Keep backups current regardless of what the numbers say — diagnostics reduce surprise, they do not prevent failure.

Frequently Asked Questions

Can bad sectors be repaired?

Logical errors can often be cleared by rewriting the affected sectors. Physical damage cannot be repaired — the drive only maps it out and continues with spare capacity.

Do SSDs get bad sectors?

They develop failing flash blocks, handled internally by the controller. For SSDs, watch wear and remaining-life indicators rather than sector counts.

How long does a surface scan take?

Roughly as long as reading the whole drive — under an hour for a small SSD, several hours for a large mechanical disk.