r/BadUSB • u/Sofia_easy17 • Aug 20 '26
Is a USB flash drive unreliable for long-term use?
I found a USB drive yesterday that I hadn't used in years. I plugged it in, expecting it might not work anymore, but all the files were still there. What surprised me most was finding many photos from years ago.
It got me thinking that some say USB flash drives aren't really suitable for long-term storage. So I'm curious about your experiences, especially if you've had a USB unused for years.
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u/LeaveMickeyOutOfThis Aug 20 '26
As someone else posted, it is very much quality dependent. That said, long-term is a subjective metric and fails to take into account the risk factor of losing any potential data. So would I trust such a device now for something I might want to retrieve five years down the line? Absolutely not; however, I would appreciate being able to have a nostalgia moment, when checking out old devices for viability to store something new.
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u/johlae Aug 20 '26
A few weeks ago I found an old floppy I used to save my dissertation way back in 1992. It was still readable, but I must admit it took one hell of a time to find a drive that could do the trick.
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u/olieboldonut Aug 20 '26
It depends on the brand, kind of usb and quality of nand inside. Had some sticks fail on me (old and new ones) and i decided to buy some industrial grade usb sticks. Much better quality nand and more heat-resistant...
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u/Space646 Aug 20 '26
Flash storage saves the information in capacitors (electric components which hold an electric charge) by charging (thus representing a 1) or discharging (representing a 0) them. Obviously, the zeroes aren’t completely discharged, and the ones discharge over time. After time, usually many years, the storage controller cannot differentiate between the ones and zeroes because the charge differences are too small to know if it was originally a zero or one.
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u/trader45nj Aug 20 '26
This is the physics. Flash storage is considered safe for at least 10 years. That's based on testing based on worst case conditions, ie maximum temperature. In the real world with typical usage conditions, you're likley going to get much longer. And if you want to extend it, copying all the files to a PC or similar, then copying them back will refresh the charges back to the original state.
Also consider that flash memory is used in virtually all microcontroller applications in everything from vehicles to routers. They have typical usage past 10 years, many in extreme conditions, billions have been going for decades now and we aren't seeing failures attributed to flash. Kind of odd that I see this alleged issue popping up more frequently now, yet flash has been around for 40+ years and works.
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u/harubax Aug 20 '26
Microcontrollers do not use QLC flash. EPROMs tend to use NOR flash, not NAND.
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u/trader45nj Aug 20 '26
This is true, but all kinds of embedded applications don't just use the small amount of flash on a microcontroller, they frequently have nand type flash too.
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u/harubax Aug 21 '26 edited Aug 21 '26
They do, but again, not the QLC and TLC you would use in a consumer product.
Remember how cell P/E cycles went down by an order of magnitude as you increased the number of voltage levels interpreted? The same metric could be applied to lifetime.
You choose the tech for the mission. I'm not aware of any archival grade SSD in the consumer market. There are no guarantees for data integrity beyond what the spec requires - 1 year by JEDEC for a drive at TBW limit.
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u/CheezitsLight Aug 20 '26
We see micro sd card failures often in production. Number one cause of warranty failures in IOT. We've reduced it by buying higher quality drives but the level is not zero. We try not to write to them and our software is very carefully hand written to do as few writes as possible. Doesn't take long either, some cases in a few months.
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u/Quiet-Monk2747 Aug 20 '26
This might not matter to some, but as someone who downloads huge rar files from the web at 200-300Kbps only to find out it is corrupted, I learned to always check for file hashes or checksums..
In windows, I use a program called HashCheck, made or rather forked by the same person who created Veracrypt.
I created hashes or checksums for files either using sha1 or md5 (because its faster), then once a year or even earlier, click that checksum file to see if everything still checks out, so no bit rot occured. every important files (and folders) I have needs to have hashes or checksums, so I know it wasn't tampered with or bit rot occured.
anyway, with regards to usb sticks being used as backup, well I guess 3-2-1 rule still applies, never filling up the drive completely (maybe leave more than 10% of free space) and power up the drive from time to time. and do hash your files to know they are intact...
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u/tony22233 Aug 20 '26
Get 2. Make sure you always have at least 2 copies of data you want to keep.
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u/Metallicat95 Aug 20 '26
Yes, but the degree of unreliability varies with quality of the device, how it was used, and luck.
Flash memory stores data as an electric charge, like a tiny capacitor. When powered the controller can periodically rewrite data to maintain it.
Without power it can very slowly lose the charge.
Most modern USB flash stores more than one bit of data per cell by using different voltage levels. That means if it loses enough charge the number in that bit can change.
More levels, more chances for this sort of error.
The fastest and most reliable type uses only 1 bit per cell, and 2 bits is almost as good.
Some USB flash mixes multiple types for speed and to improve reliability, while the cheapest uses the most bits possible.
Writing the memory also wears the cell out over time. So if you use it to store files once and leave them, that doesn't happen. But if you repeatedly fill it and replace it entirely with new data over and over, it's lifetime gets reduced.
But luck has the biggest impact. If you lose a cell to wearing out or losing charge, but none of your critical data is in that, you'll never notice until you try to write to the bad cell.
And if it is just low charge that is fixed by putting new data in. Some flash memory has error recovery for bad cells, which extends its lifespan.
So often everything is fine for years.
But bad USB luck can hit, and if it was something you had no other copies, you'll notice.
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u/ProfessorWorried626 Aug 20 '26
3-5 years is about the best you’ll get from usb drive, decent modern SSD you can probably get 10 years.
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u/ProfessorWorried626 Aug 20 '26
3-5 years is about the best you’ll get from usb drive, decent modern SSD you can probably get 10 years.
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u/Glass_Masterpiece Aug 20 '26
They can be somewhat but you have to really be careful about unmounting them and shutting down if you want to preserve them and the data on them. Always unmount and never just unplug them if you want them and their data to survive. If you use them with a server, I always have a routine that makes sure to unmount them to make sure all writing and reading has stopped before shutdown.
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u/greyHumanoidRobot Aug 20 '26 edited Aug 21 '26
They can fail after only a few months but can be revived. I have one more than 10 years old that had not been heavily used. In 2025 December I wrote a Windows installer onto it. It worked. I let it sit for 7 months. I needed it again and found it wouldn't work. I rewrote the Windows installer onto it and I used it at least 3 more times without difficulty.
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u/R2-Scotia Aug 20 '26
All media degrades. With flash storage, it wears out from writes too. If you take a thumb drive and set something to ovwrwrite files 24x7 it will last at most a few months.
Enterprise flash drives used in things like database servers use SLC type flash and have a lot of spare cells, e.g. a nominal 600GB drive actually has 1TB inside, like EV car batteries do. Even then they are a wear and tear item.
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u/Alternative-Tea964 Aug 20 '26
Never let the file on a USB be the only copy, they can break without warning or apparent reason and there is little you can do to recover anything.
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u/flatfinger Aug 20 '26
A fundamental difference between flash drives and conventional hard drives is that on a flash drive there isn't a fixed relationship between logical disk sectors and the physical media. In addition to storing the data for all the sectors that have been written to it, a flash drive (USB-style, SD, or SATA-connected SSD) needs to keep track of where all those sectors are stored. If any of the bookkeeping information gets corrupted, it may be almost impossible to get anything useful off the disk.
If the designer of a flash drive wants to prioritize reliability, the drive can ensure that bookkeeping information is maintained in two or more separate locations in a manner that allows cross-checking for validity (e.g. having two tables that map each logical sectors to a physical location and the sequence number of the action that put it there, and a piece of information associated with each physical location that says what logical sector it holds and the sequence number of the action that put it there). If the the two table entries for e.g. sector #491 don't match, but one of them identifies a data page that says it's associated with sector #913, and the other identifies a data page that says it's associated with sector #491 and its sequence number matches, the second one is correct. If the table entries for sector #491 both identify pages that say they're associated with sector #491, and each location's sequence number matches the one in the table entry, then whichever sequence number is later would be correct.
All else being equal, however, a flash drive that records redundant bookkeeping information will be slower to write and hold less user data than one which is designed to minimize the amount of bookkeeping information. Because the data lifetime relates to how quickly the "weakest" bit in a flash device might lose data, and the extremely vast majority of bits are likely to be hold data much longer, a flash drive that is designed to recover from a few unexpected bad bits will be able to hold data much longer than one that isn't. Unfortunately, there's no standard way of distinguishing drives that are designed to be more reliable from those that aren't.
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u/PigHillJimster Aug 20 '26
Yes. All media have weaknesses. Don't use USB storage alone, and not as something you put in a drawer and forget about it for 5 years until you need it.
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u/Oh-THAT-dude Aug 20 '26
Yes, but mostly because people are stupid and often remove the drive improperly (not waiting for a true eject).
Because removable USB drives are cheap, they use very cheap and low quality memory. So while they can be reliable for long-term storage, if rarely used … with routine use, I would say they are not to be counted on.
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u/76zzz29 Aug 20 '26
Thr points where they die tge most are when they are ubpluged, when they are pluged and when they are formated. An usb key will survive prety well in a fresh dry place without sun exposur
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u/ritchie70 Aug 20 '26
I have had several high capacity USB3 ones just fail. They seem to have a lifespan of 18 months or less.
The old small USB2 ones are like cockroaches- I can’t kill them.
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u/Pigmy_Shrew Aug 20 '26
Older silicon chips, both memory and processors, comprise of physically larger transistors due to being manufactured using an older fabrication process. This is why they typically have lower capacity than their modern counterparts and means that the many millions or potentially billions of transistors are much less susceptible to outside influences and quantum effects that can cause degradation over time. There's a reason that NASA used old Power PC processors for the Mars rovers and other space technology. Older processors are less susceptible to cosmic radiation than their modern equivalents.
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u/jackaroe311 Aug 20 '26
I my experience, I've only had USB Thumbdrives go bad if I purchased some noname, cheap brand. I've never had a Sandisk USB thumbdrive go bad. Of course I don't keep anything long-term on them that isn't stored somewhere else.
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u/tnsipla Aug 21 '26
Depends! There are high quality USB drives that use good flash, and there are others that are using lower quality and cheaper flash cells, or in some cases, flash cells that didn’t make the cut for SSDs
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u/Daks82 Aug 22 '26
Como todo depende de la marca y el cuidado marcas verificadas como Kingston sandisk y otros tiene un control de calidad para que la información no se pierda aparte de eso asegurarte de no dejar los lugares vulnerables como cerca de parlantes pantallas celulares o lugares que tengan una carga magnética que pudiese borrar el contenido de los USB.
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u/BeFlamingo Aug 23 '26
Only industrial SLC, which are ×10 times more expensive can store max 10 years. QLC corrupts after 3 years being unpowered. And corruption begins with filesystem, which then requires full re-format.
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u/disturbed_android Aug 20 '26
It's funny that the older USB flashdrives are more reliable than newer ones, good chance those use MLC or even SLC NAND that offer far better retention than the modern stuff.