On 10/23/2019 11:26, Dave wrote:
> On 23/10/2019 15:14, Knute Johnson wrote:
>> You will never wear out a uSD card from writing to it.  From the
>> SanDisk SD Card Product Manual.
>>
>> https://www.manualslib.com/manual/587744/Sandisk-Sdsdb-016g-A11.html
>>
>>
>>> 1.8
>>> Endurance
>>> SanDisk SD cards have an endurance specification for each sector of
>>> 100,000 writes typical
>
> Careful. That document dates from 2004, when single-bit-per-cell devices
> were all that was available. The most recent cards are 4-bit-per-cell
> and with cell sizes much smaller to increase the capacity per chip. I
> believe that around 1000 writes per cell is all that can be expected
> nowadays.
>
> However like many others, I have never had an SD card fail. I have one
> which has been in constant use for about 4 years as a Pi system disk.

A 32GB card written to 1000 times is 32TB.  Write 1 million bytes per
second to the card, 24/7/365 is 31.536 trillion bytes.  So at a million
bytes per second the card will last a year.  At only a thousand bytes
per second the card will last a thousand years.  Unless you are doing
something really strange you aren't going to write to it that much.

But I had a thought, I'm going to get a new card and set up a Pi on a
UPS and write to it as fast as I can till it dies.  It won't really tell
us much but it could be interesting anyway.

--

Knute Johnson

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