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.

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