Capacity rollover errors after connecting a hub

Your USB drive or SD card reports the expected size, but files fail or become corrupted after you connect it through a hub. That can point to a connection problem, a faulty reader, or storage that reports more capacity than it can really hold.

Test the drive by itself before replacing it. The Fake USB & SD Check fills the removable drive with test data and reads it back, which can reveal whether the advertised capacity is usable. It works in Chrome and Edge on a computer.

Check the drive and hub

1. Back up anything you need from the USB drive or SD card. The capacity check writes a large amount of data, so do not use it on the only copy of important files.
2. Open the Fake USB & SD Check in Chrome or Edge on a computer. Follow the on-screen instructions to choose the removable drive you want to test. Do not select your computer's internal drive.
3. Let the check finish without removing the drive or closing the browser. A full-capacity test can take a while, especially on a large or slow card.
4. Note whether the check completes, reports read-back errors, or stops when the drive disconnects. If it fails, repeat the test with the drive connected directly to the computer rather than through the hub.
5. If the result changes when you bypass the hub, test another hub port or reader, and try the same drive on another computer if available.

Use the same drive and the same test conditions for each comparison. If the test reports errors, do not keep copying valuable files to it until you have another safe copy.

What the result means

The test reads back the data successfully

The drive stored and returned the test data across the capacity the check examined. That makes a fake-capacity problem less likely, but it does not prove the drive will remain reliable over time or that every file system and device will work with it. If the original problem happens only through the hub, focus on the hub, cable, or card reader.

The check reports errors after a certain amount of data

This often means the drive cannot reliably store data across its claimed capacity. A counterfeit drive may report a large size while containing much less real flash storage. Once writes go beyond that real capacity, they can overwrite earlier data or fail, which may make files disappear or become unreadable. A worn or defective drive can also produce errors.

The check fails only while the drive is connected through the hub

The hub, its cable, the port, or the reader may be interrupting the connection. A hub-related failure by itself does not prove the drive has fake capacity. If the same drive passes when connected directly, the hub path is the stronger suspect.

The drive disconnects or the check stops immediately

The computer may be losing contact with the drive, or the reader or hub may not be supplying a stable connection. A damaged connector, loose cable, or failing drive can cause the same symptom. Compare a direct connection and a different port before drawing a conclusion.

How to fix the problem

1. Stop writing new files. If files are disappearing or changing, stop using the drive and copy readable files to another trusted device. Avoid repeated tests until anything important is backed up.
2. Connect the drive directly. Remove the hub from the path and plug the USB drive or reader into a computer port. For an SD card, try a different card reader as well. Eject the drive before unplugging it.
3. Try another port and cable. A loose USB connector or damaged hub cable can cause brief disconnects. Use a port on the computer itself and avoid daisy-chaining hubs during the test.
4. Check that the computer sees the expected drive. On Windows 11, open File Explorer and check the drive under This PC. On macOS, check the drive in Finder. The displayed size is only what the device reports, not proof that all of its space works.
5. Repeat the read-back check on another computer. If the error follows the drive when connected directly to another computer and reader, the drive itself is likely faulty or misrepresenting its capacity.
6. Replace a drive that fails consistently. Do not rely on formatting to repair a capacity rollover problem. Formatting changes the file system, but it cannot add real flash storage or fix failing memory.

When the drive is the problem

If the check repeatedly finds read-back errors at a similar point, even with a direct connection and another reader, treat the media as unreliable. Copy off any files that are still readable, then return the drive if it is under warranty or replace it. A card or flash drive that has already corrupted files should not be trusted for backups, camera footage, or other irreplaceable data.

If the drive passes directly but fails through one hub, replace or stop using that hub or reader for important transfers. You can compare with another hub, but do not assume a passing test means a questionable hub is safe for every device or file transfer.

Why capacity rollover can corrupt earlier files

A counterfeit drive can tell the computer that it has more storage than is physically present. When a write reaches the actual limit, the device may wrap around and write over data stored at the beginning, rather than reporting that it is full. The computer can still show the advertised capacity, so checking the label or the size listed in File Explorer or Finder is not enough.

Capacity and connection problems can also happen together. A hub can interrupt a long test, while a fake or failing drive can cause read-back errors even when connected directly. Compare the same drive through a direct port and another reader to separate those causes.

The check runs in your browser and works with the removable drive you select. Keep a separate backup of important files before testing storage.