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Unexpected USB Size


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#1 tsrplatelayer

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Posted 27 April 2017 - 03:21 PM

Long time PC user ( I had the first IBM AT sold in the uk on my desk!)

Experienced Hardware, software and worked in user tech support until retirement.

Now running WIn 10 on a desktop at home.

 

I have been having problems with an 8Gb memory stick. I bought a pack of 3. 2 of them work OK, The third has started giving errors.

I tried reformatting and noticed that the 2 that work have 7,45GB capacity whereas the one that doesnt has 7,25GB capacity.

Using WIndows 10 disk manager showed that the 'faulty' one had a single partition, I used DISKPART to Clean /Repartition/ Reformat - it still has the odd size.

I used Active Partition Manager (APM) to examine the USB sticks. The 'faulty' one has an unidentified small partion that I cannot delete or in any way change with APM.

I cannot format it.

Here is the APM partition status:

  Primary: [not ready] (I:), 0 bytes [Unknown]

    General

      Name..............................[not ready] (I:)

      Type..............................Primary

      Active Partition..................Yes

      File System.......................Unknown

      RAID Type

 

    Partition Geometry

      First Sector......................0

      Offset............................0

      Segment...........................0

      Bytes per Sector..................512

      Total Sectors.....................0

 

    Volume: [not ready] (I:), 0 bytes [Unknown]

      Volume General

        Volume name

        Volume letter...................I

        Volume type.....................Volume

        File system.....................Unknown

        Serial number

        GUID name.......................\\?\Volume{272c2b0f-25a9-11e7-838b-9cb654f8b704}

        Scanned.........................No

 

      Volume integrity info

        Overall integrity status........Invalid

 

      Volume capacity

        Total size......................0 bytes (0 bytes)

 

      Volume Geometry

        First sector....................0

        Total sectors...................0

        Bytes per sector................512

        Cluster size....................512 bytes

        Get max file size...............0 bytes (0 bytes)

 

 

MBAM and Avast detect no problems on my system.

 

I know that Windows doesnt support partitions on removable media so I am concerned that this unwanted/unexpected partition may have been hijacked by something malicious, or could it be SanDisk using it to 'map out' faulty blocks?

 

Still waiting for San Disk after a couple of weeks since I emailed them - any advice appreciated.



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#2 JohnC_21

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Posted 27 April 2017 - 06:09 PM

How is the USB drive shown using Gparted? It's based on linux. You can download the live version here

 

Make sure to pick the correct device in the dropdown box.

 

gparted-choose-device.jpg

 

You can also dd in terminal to zero out the flash drive then partition and format. Be very careful using the dd command. Make sure you input the correct device. You don't need sudo using the Gparted Live disk.

 

https://askubuntu.com/questions/185815/how-do-i-clear-everything-data-viruses-from-a-thumbdrive


Edited by JohnC_21, 27 April 2017 - 06:17 PM.


#3 tsrplatelayer

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Posted 28 April 2017 - 03:14 AM

Created bootable USB but will not boot, Disabled UEFI enabled legacy, set boot disk as priority and disabled secure boot - but still wont boot this Linux unit. I'll try a CD

 

CD ISO created - booted and Opening screen displayed but would not accept input from wireless kybd/mouse


Edited by tsrplatelayer, 28 April 2017 - 03:53 AM.


#4 tsrplatelayer

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Posted 28 April 2017 - 06:50 AM

Tried Rufus USB format tool - no go. Tried TestDisk - no go. I cannot get rid of this partition.

I have located a wired KYBD to back to Linux again



#5 tsrplatelayer

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Posted 28 April 2017 - 07:20 AM

Managed to get GPartEd Live working - had to use fail safe. I had 2 identical memory sticks installed.

1 device that works is size 7 998 799 872 bytes

1 that has a stray partition in Active Partition Manager is size 7 812 325 376 bytes

 

GPartEd recognised both.

The working one was recognised as

MSDOS, 255 heads, 63 Sectors/Track, 972 Cylinders, 15630336 Total Sectors, 512bytes/sector

It had a single full size valid partition

 

The other one was recognised as

MSDOS, 255 heads, 63 Sectors/Track, 951 Cylinders, 15293440 Total Sectors, 512bytes/sector

no partitions, all unallocated.

 

Clearly 21 Cylinders are missing.

 

I didnt try DD - Linux is unknown to me sadly.



#6 JohnC_21

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Posted 28 April 2017 - 07:35 AM

If Gparted shows the one USB as unallocated but with fewer total sectors then I would think the flash drive has for some reason marked some sectors as bad. Even if using dd you would still get the same sector count of 15293440.

 

Partition Wizard has a wipe disk setting but I am not sure it will work on the USB flash drive. It essentially does what dd does. 

 

Edit: This link may describe the sector count discrepancy. I have a 32GB USB flash drive with 100MB of sectors that are "missing".

 

https://superuser.com/questions/892109/why-45mb-unallocated-space-at-the-beginning-of-a-silicon-power-marvel-m70-64gb-f


Edited by JohnC_21, 28 April 2017 - 07:41 AM.


#7 tsrplatelayer

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Posted 28 April 2017 - 07:46 AM

Thanks for the input - I have now tried DD. GPartEd now shows a warning triangle  and still has the reduced sector count as you suggested. I just had a reply from SanDisk Tech

"

All SanDisk® products include the total capacity, at an unformatted level, that is stated on the product packaging. For example, a 128GB SanDisk USB flash drive has a total capacity of 128,000,000,000 bytes at the unformatted level (where 1GB=1,000,000,000 bytes).

 

A portion of the total capacity is used to store certain functions including optimizations of the memory that support performance and endurance and therefore is not available for user storage. This is disclosed on our packaging and marketing materials when you see the statement “Actual user storage less.”

As a leader in flash storage technology, we offer multiple products at different speeds and capacities to address a variety of consumer needs. To provide the optimum product for you, we’re continuously improving and updating our technology, products, firmware, and design. Continual improvements and updates are made to our product (both new products and existing product lines) and can include changes to the basic file structure, formatting and other functions. These optimizations may result in variances as to the amount of memory space that is available for user storage, but are essential to performance and endurance of the products.

"



#8 JohnC_21

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Posted 28 April 2017 - 08:56 AM

Thanks for the update. I would have to assume from the link I posted and your feedback from Sandisk that your flash drive is not infected and is just a matter of blocking off sectors that cannot be read.



#9 tsrplatelayer

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Posted 28 April 2017 - 12:46 PM

Thats what I have assumed but a loss of 0.5GB out of 8GB seems a bit excessive after only 2 months so I have requested a replacement - lets see if they hide behind the'our packaging says the size may be smaller' clause






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