How to check the health status of a USB stick?

How do I know that a USB is broken beyond repair, or repairable?

  • 14
    Throw it away. Your invested time is more expensive than buying a new one.
    – mailq
    Jan 8 '12 at 23:29
  • 2
    I have to agree with @mailq. You can buy a decent 4 GB thumb drive for $2.00 these days.
    – iglvzx
    Jan 9 '12 at 6:24
  • 22
    @iglvzx Well the question does not tell, if it is a cheap one, or some +32Gb encrypting fast one...
    – varesa
    Jul 26 '12 at 15:34

There is no way to query a USB memory stick for SMART-like parameters; I'm not aware of any memory sticks that support doing so even via publicly-available proprietary software.  The best you can do is to check that you can successfully read+write to the entire device using badblocks.


You want to specify one of the write tests, which will wipe all data on the stick; make a backup first.

Find the device by looking at dmesg after plugging in the USB stick; you'll see a device name (most likely sd<letter>, e.g., sdc, sdd, etc.) and manufacturer information.  Make sure you're using the proper device!

If the stick is formatted with a valid filesystem, you may have to unmount it first (with the umount command).

Example syntax, for a USB stick enumerated as /dev/sdz, outputting progress information, with a data-destructive write test and error log written to usbstick.log:

sudo badblocks -w -s -o usbstick.log /dev/sdz

You'll need to repartition and reformat the stick afterwards, assuming it passes; this test will wipe everything on the stick. Any failures indicate a failure of the device's memory controller, or it has run out of spare blocks to remap failed blocks. In that case, no area of the device can be trusted.

  • 27
    badblocks is probably the best option. the comments that say "not worth it" completely miss several cases when this can be very needed (for example, a company might have purchased merchandise flashdrives, and would like to see how badly they got scammed...)
    – Richlv
    Jul 25 '12 at 17:18
  • 2
    as pointed out in the wikipedia article linked, there's also e2fsck -c that uses badblocks and effectively hides those badblocks from the filesystem, thus avoiding corrupted writes. It should be noted however that, if the disk got new badblocks it's probably getting damaged and new ones may arrise later, meaning its life is shortening and you should consider replacing it. Aug 13 '14 at 4:19
  • 1
    I suggest adding the -v flag as well do see the error in the terminal windows. (if you let it run over night for example. The logfile is not that helpful for a quick view how bad it is.
    – Tilo
    Dec 17 '14 at 15:49
  • @BeeDee, should we use whole device or just some partition or it does not matter? I mean /dev/sdz or /dev/sdz1?
    – Mr. P
    Feb 13 '15 at 8:45
  • 1
    @Pisek you ought to use whole device, because it is the device failing, not just a partition.
    – Hi-Angel
    Apr 5 '15 at 22:03

Via [ubuntu] Error Check USB Flash Drive, I eventually found this, which could be helpful:

I arrived at the blogs Fight Flash Fraud and SOSFakeFlash, which recomend the software H2testw (see here or here) to test flash memories. I downloaded H2testw and found two issues with it: (1) it is for Windows only, and (2) it is not open source. However, its author was kind enough to include a text file that explains what it does; this page is about my GPLv3 implementation of that algorithm.
My implementation is simple and reliable, and I don't know exactly how F3 compares to H2testw since I've never run H2testw. I call my implementation F3, what is short for Fight Flash Fraud, or Fight Fake Flash.

Addendum by @pbhj: F3 is in the Ubuntu repos. It has two part, f3write writes 1GB files to the device and f3read attempts to read them afterwards. This way capacity and ability to write and effectively read data are tested.

  • 4
    Is there any advantage to F3 over badblocks?
    – Zaz
    Jul 15 '14 at 13:41
  • 6
    @Zaz As best as I understand it, badblocks isn't designed for detecting fake flash drives and may not report any errors for them.
    – bmaupin
    Aug 28 '15 at 19:50
  • I see some advantages for a typical user: (1) it detects (quickly) a fake flash, which as @bmaupin mentioned badblocks can't do reliably (nor quickly), and is able to "fix" a fake flash, (2) to check full drive health, it is comparable to badblocks, but it doesn't require root privileges and it gives a slightly more nuanced output, (3) if you don't need to check all sectors, you don't have to completely erase and reformat the drive.
    – Piotr
    Sep 30 at 11:07

It depends on the failure mode, I suppose. They're cheap for a reason.

As a USB device, watching the bus via device manager in Windows or the output of dmesg in Linux will tell you if the device is even recognized as being plugged in. If it isn't, then either the controller on board or the physical connections are broken.

If the device is recognized as being plugged in, but doesn't get identified as a disk controller (and I don't know how that could happen, but...) then the controller is shot.

If it's recognized as a disk drive, but you can't mount it, you might be able to repair it via fdisk and rewrite the partition table, then make another filesystem.

If you're looking for the equivalent of S.M.A.R.T., then you won't find it. Thumbdrive controllers are cheap. They're commodity storage, and not meant to have the normal failsafes and intelligence that modern drives have.


Along the way to today, this thread raised some questions.

-How long will this take (implied by discussion of letting it run overnight).

I'm currently testing a USB 3.0 128G Sandisk using sudo badblocks -w -s -o, it is connected to my USB 3/USBC PCIe card in an older Athlon 64x2. So, USB3 into USB3 on PCIe should be quite fast.

Here is my console command line at 33% completion:

Testing with pattern 0xaa: 33.35% done, 49:47 elapsed. (0/0/0 errors)

and again later:

Testing with pattern 0xaa: 54.10% done, 1:17:04 elapsed. (0/0/0 errors)

Next came this segment:

Reading and comparing: 43.42% done, 2:23:44 elapsed. (0/0/0 errors)

This process repeats with oxaa, then 0x55, 0xff, and finally 0x00.

ArchLinux gave an unqualified statement:

For some devices this will take a couple of days to complete.

N.B.: The testing was started about 8:30 p.m., testing had completed before 8:45 a.m. the next day, completing in about 12 hours for my situation.

-Destructive testing isn't the only method possible.

Wikipedia offered this statement:

badblocks -nvs /dev/sdb This would check the drive "sdb" in non-destructive read-write mode and display progress by writing out the block numbers as they are checked.

My current distro man page confirms the -n is nondestructive.

-n Use non-destructive read-write mode. By default only a non- destructive read-only test is done.

And finally that it isn't worth it. statement.

A summarizing statement, based on the situation of billions of memory sites in a flash chip, a failure is a cell that has already been written and erased tens of thousands of times, and is now failing. And when one test shows a cell has failed, remember that each file you added and erased is running up those cycles.

The idea here is that when 1 cell fails, many more cells are also reaching the same failure point. One cell failed today, but you use it normally for a while longer, then 3 more cells fail, then 24 more fail, then 183, and before you know it, the memory array is riddled with bad spots. There are only so many cells that can die before your usable capacity begins to fall, eventually falling rapidly. How will you know more cells are failing? So, posts here are guarding your data by saying once you have a bad cell, you are pretty much done in regards trustworthy storage. Your usage might still give you a few months.

It's your data.


  • This answer is riddled with incoherences. First, you're talking about the long testing time, then advocate for the -n option which is officially described as even slower than -w. Furthermore, it obviously won't test sectors where data is already present (from the filesystem's viewpoint), thus can't reliably determine the failing status of a drive, cause as you said 1 bad block or 1000 is the same from a human standpoint, and a coincidence can very well happen that there's only one or a few bad blocks on the sections with live data. It's absolutely not a strictly better option than -w.
    – Atralb
    Oct 13 '20 at 15:40

Many failures are either complete or allow one location to support multiple locations. I wrote a little random write read program that uses a prime number for a pseudo-random number generator, for both patterns and addresses. The reads are staggered behind the writes by enough pages to ensure I am not testing ram cache on the system. It is not yet parameterized, just set up for a 64G device on my system with 8G ram. Feel free to criticize, parameterize, make it smarter.

This is a powerful check and faster than doing every byte bottom to top, but is also a great swap generator (rolls almost everything else out). I put swapiness at 1 temporarily and it became slower but more tolerable to other apps. Any tips on how to tune against swapout would also be appreciated:

$ sudo ksh -c 'echo 1 > /proc/sys/vm/swappiness'

$ cat mysrc/test64g.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>

int main( int argc, char **argv ){

        long long int mask = 0xFFFFFFFF8L ;    // 64Gb word
        long long int stag = 8413257 ;  // 8G / 1021
        long long int inc = 1021L ;     // prime < 1024

        long long int w_addr = 0L ;
        long long int r_addr = 0L ;
        long long int w_ct = 0L ;
        long long int r_ct = 0L ;
        long long int w_patt = 0xFEDCBA9876543210L ;
        long long int r_patt = 0xFEDCBA9876543210L ;
        long long int r_buf ;
        int fd, ret ;

        if ( argc < 2
          || argv[1] == NULL
          || 0 > ( fd = open( argv[1], O_RDWR ))){
                printf( "Fatal: Cannot open file $1 for RW.\n" );
                exit( 1 );

        while ( 1 ){
                if ( (off_t)-1 == lseek( fd, w_addr & mask, SEEK_SET )){
                        printf( "Seek to %llX\n", w_addr & mask );
                        perror( "Fatal: Seek failed" );
                        exit( 2 );

                if ( 8 != ( ret = write( fd, (void*)&w_patt, 8 ))){
                        printf( "Seek to %llX\n", w_addr & mask );
                        perror( "Fatal: Write failed" );
                        exit( 3 );

                w_ct++ ;
                w_addr += inc ;
                w_patt += inc ;

                if ( ( w_ct - r_ct ) < stag ){
                        continue ;

                if ( (off_t)-1 == lseek( fd, r_addr & mask, SEEK_SET )){
                        printf( "Seek to %llX\n", r_addr & mask );
                        perror( "Fatal: Seek failed" );
                        exit( 4 );

                if ( 8 != ( ret = read( fd, (void*)&r_buf, 8 ))){
                        printf( "Seek to %llX\n", w_addr & mask );
                        perror( "Fatal: Read failed" );
                        exit( 5 );

                if ( ( ++r_ct & 0XFFFFF ) == 0 ){
                        printf( "Completed %lld writes, %lld reads.\n", w_ct, r_ct );

                if ( r_buf != r_patt ){
                        printf( "Data miscompare on read # %lld at address %llX:\nWas: %llX\nS/B: %llX\n\n", r_ct, r_addr & mask, r_buf, r_patt );

                r_addr += inc ;
                r_patt += inc ;
  • Using a inc of a power of 2 like 1024 would allow better checking or dead high address bits, although only checking 8 bytes per hop. Aug 14 '15 at 20:02
  • yeah, this will miss the case of dead high bits. also doing reads and writes in the same pass can miss that,
    – user313114
    Nov 25 '15 at 20:47
  • Another simple check is to write a 3 byte rotating pattern 3 times, like 0x49, 0x92, 0x24, since addressing errors and lies about size have mod-2 signatures. After one writte read pass, roatate the rytes and repeat, twice. The third byte tests parity on, if any. For edac, more patterns and / or longer words are needed, but the non-mod-2 rotation count still applies. Aug 27 '20 at 20:10

Nobody seems to have mentioned a failure variant I ran into - a more general controller/interface failure.

When you plug a USB device in, it will generate some lines in dmesg. e.g.

 [ 3209.991107] usb 2-1.1: New USB device found, idVendor=0951, idProduct=1666
 [ 3209.991117] usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
 [ 3209.991123] usb 2-1.1: Product: DataTraveler 3.0
 [ 3209.991129] usb 2-1.1: Manufacturer: Kingston

You can then run: lsusb

For more info you can focus on the Vendor ID:Product ID

lsusb -d -v 0951:1666

If your drive has been probed and recognised by the kernel you'll see a new /dev/sd? entry for a block storage device. If it hasn't automounted a filesystem, you can try to access the filesystem structure (as opposed to content):

e.g. mount /dev/sdb1 /mnt

In my case I had a fritzed controller on a new USB stick rather than dying NAND cells on an older one...

dmesg spat this out a while later, amongst many other messages:

[ 3356.078359] usb 2-1.1: new high-speed USB device number 36 using ehci-pci
[ 3361.098287] usb 2-1.1: device descriptor read/8, error -110
[ 3366.217872] usb 2-1.1: device descriptor read/8, error -110  
[ 3366.321702] usb 2-1-port1: unable to enumerate USB device

So, for me, once I'd finally got the USB filesystem mounted, half way through an fsck (to walk more NAND cells) it keeled over entirely and never came 'online' again!

Look for Krzysztof Opasiak - Debugging Usually Slightly Broken (USB) Devices and Drivers on UTube

Hope this adds a little more useful background, beyond the dying NAND cells scenario.

  • 1
    I don’t understand.  What do mount and fsck have to do with diagnosing the health of the hardware? … … … … … Please do not respond in comments; edit your answer to make it clearer and more complete. Jan 20 '20 at 22:12

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