On 2019-11-01, Knute Johnson  wrote:
> On 10/30/2019 2:26 PM, Henri Derksen wrote:
>> Hello Knute,
>>
>>> Following a discussion on another thread about the life limits of an
>>> SDCard I thought I would write a program to write one to death and see
>>> just how long it lasts.
>>
>>> I'm running some tests now on an old card I had lying around.  I am
>>> going to order some new cards once I am sure I have the right test
>>> going.
>>
>>> I would appreciate comments on the testing algorithm and on my code if
>>> you have any.
>>
>> Your test consists of files always the same length, and same contents.
>> I do not think that is a realistic test.
>> First you could use random file-lenghts and contents, i.e. all figures from
0
>> to 255 up and down etc.
>
> I wanted to write as many bytes as possible and do it quickly because I
> figured it would take a while.
>
>> But there is a more drastic way of testing.
>> Use two micro-SDcards of the same size and make and two SDcard readers.
>> Fill one completely until it is almost full except a few byts unused.
>> Then make a copy with DD to the other card, i.e. a full backup.
>> After that lowlevel format the destionation card, so its is really empty,
>> and make again a full backup of the first card, etc..
>> Then count the amout of perfect copies without errors, and also the time
>> every backup copy takes.
>> As soon as you get much longer backup times and/or many errors,
>> you know the destination card died. Then look at the BackUp counter,
>> how many copies were made and in how much time?
>> Does that sound more realistic?
>
> I wanted to use a scheme that was similar to regular use except a lot
> more of it so I could kill it in a shorter period of time.  I think your
> idea would certainly give you valid data but I'm not sure how to apply
> that to what we want to find out which is how long will a micro SD card
> last in normal use.
>
>> By this way of testing, you almost completely mislead the anti wear
techniques,
>> as you only copy full discs and erasing them and so on.
>> After the test you know how many backups could be made safely with the same
>> media.
>> Good luck in testing.
>>
>> Henri.
>
> Thanks for looking at it Henri.

This command pipeline writes 233MiB/s to /dev/null on my main
home system (nearly a decade old).  I suspect it would be faster
than any practical SD card or USB stick could handle.  It writes
decimal text representations of numbers but with no repetition.

    yes '' | cat -n | tr -d ' \t' | pv -prb

HTH

--
Robert Riches
spamtrap42@jacob21819.net
(Yes, that is one of my email addresses.)

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