How the fake-capacity scam works
A counterfeit drive's controller is programmed to report a large capacity to your computer — say 1TB — while the actual flash chip inside might be 8GB or 16GB. Everything looks fine at first. But once you write past the real capacity, the drive silently wraps around and overwrites data you already stored. You often don't discover it until a photo or document you saved months ago is corrupt.
Warning signs before you even test
- A price that's far too good for the advertised size.
- Marketplace listings with vague brands and huge capacities.
- Capacity that seems implausibly large for the physical size or price.
How to actually test it (free, a few minutes)
You can't trust the size the drive reports — you have to write verifiable data across the whole claimed capacity and read it back. Cinder's free Drive Integrity & Capacity Test does exactly that:
- Fast Boundary Probe writes markers at doubling offsets and binary-searches for the wraparound — it can flag a fake multi-terabyte claim in seconds.
- Full Sequential Verify writes and re-checks markers across the entire claimed capacity for maximum certainty, the same core approach as the well-known H2testw tool.
It writes one visible, clearly-named test file you can watch in Finder, and deletes it when done. If the drive is faking its size, the test catches the moment earlier data gets overwritten.
What to do if a drive fails
Stop using it for anything important and request a refund or chargeback. A fake-capacity drive isn't repairable — the lie is in its firmware.