Lab Investigation — USB Pen Drive Endurance
How reliable are USB pen drives, really?
We bought three identical SanDisk 32GB pen drives from the same multipack and put them under continuous, randomised write testing to find out how much data NAND flash can actually take before it fails. The test is running live on YouTube — here's what the first three days show.
The premise
NAND wears out. The question is how fast.
USB pen drives and SD cards run on NAND flash memory, and NAND degrades a little with every write.
In our experience, USB pen drives and SD cards are not something to trust with long-term storage — failure rates climb sharply after just a few months of use. That is not bad luck; it is how the technology works. Every write cycle wears the memory chip slightly further, so failure is not a possibility, it is a certainty. The only real question is how much data a given drive can take before it happens.
To find out, we bought three identical 32GB SanDisk pen drives — a current best-selling listing on Amazon — loaded them onto a dedicated test rig, and started writing to them continuously until they fail. We're running it as a live YouTube stream, with an SSD endurance test planned to follow.
Method
Deliberately hostile conditions.
- 01
Identical hardware
Three SanDisk 32GB pen drives from the same multipack, run on a dedicated test rig with plenty of RAM and CPU headroom so the platform itself is never the bottleneck.
- 02
Hard Disk Sentinel
Continuous write testing driven through Hard Disk Sentinel, logging write speed, total data written and error count on each drive in real time.
- 03
Random block, random data
Configured for random block writes with random data — harder on the controller's ECC and XOR handling than a simple sequential copy, and enough to defeat the caching that would otherwise flatter the numbers.
- 04
Pass after pass
Each drive is filled and rewritten repeatedly — one full cycle counted as a "pass" — continuing until a drive reports write errors or fails outright.
Three days in
One drive is already falling behind its siblings.
Real-world performance and long-term durability are turning out to be two different questions.
SanDisk's spec sheet lists up to 130MB/s read and write. Under random-write testing on the first pass, we saw speeds ranging from 7MB/s to 39MB/s — nowhere close, and a reminder that advertised figures assume best-case sequential transfers, not the pattern most real usage actually produces.
Three days into continuous testing, the three drives — pulled from the same multipack — are no longer behaving identically. One is writing roughly half the data of the other two, averaging under 5MB/s against 10MB/s and 15MB/s on its siblings. Across all three, the average sits around 12.5MB/s in random-write conditions.
None of the three has thrown a write error yet. But based on the gap that has already opened up, we expect the slowest of the three — Drive 2 — to be the first to fail. We'll update this page with the final result for each drive once it happens.
What this means in practice: a pen drive can look completely fine for months while quietly approaching its actual write limit — there is no odometer warning you how close it is. Treat USB pen drives and SD cards as transport media, never as the only copy of anything that matters.
Wear-related failure behaves differently to a knock or a snapped connector, but the rule is the same either way — stop using it and get an honest diagnosis before you lose the window to recover it.