[PLUG] Weird microSD failure

[Russell Senior]

On Tue, Mar 6, 2018 at 3:01 AM, Jim Karlock <jjkarlock at gmail.com> wrote:
>
>> My initial attempt to google this was unsuccessful (most people point
>> out the write protect tab, not my problem).
>
>
> Bad switch on the write protect tab? (The tab operates a tiny switch.)

Nope.

I can turn the switch to lock and it mounts the device read only very
clearly.  The behavior I observe is that it happily writes /dev/zero
over the block device, but then when I read again, the old data is
still present.

>
> thanks
> JK
>
>
>
> At 01:25 AM 3/6/2018, you wrote:
>>
>> I started playing with my Pine 64+ quad-core ARM64 board again
>> recently.  I have a 16GB Samsung EVO microSD card I was using
>> previously.  I started out by zero'ing it:
>>
>>   dd if=/dev/zero of=/dev/sdc bs=1M status=progress
>>
>> which seemed to finish fine.  But when I remove and re-insert it, it
>> still has data on it.  Double-U Tee Eff?  I have tried the same
>> process on three different machines with different methods of
>> connection (in an SD adapter in a USB-SD reader; in the SD adapter in
>> a laptop SD slot (probably still USB internally); and directly in a
>> microSD slot in a second laptop).
>>
>> I get no warning about being read only.  The writes seem to occur
>> successfully and fully complete.  I sync before I remove the media,
>> plug it back in and all the old data is still present.
>>
>> My initial attempt to google this was unsuccessful (most people point
>> out the write protect tab, not my problem).
>>
>> Any similar experience, and/or clues for recovery?
>>
>> Thanks in advance.
>>
>> --
>> Russell Senior
>> russell at personaltelco.net
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>
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