Author Topic: SD card wear  (Read 748 times)

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Offline DG41WVTopic starter

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SD card wear
« on: September 28, 2019, 01:07:47 am »
Hi guys,

In a project I'm doing I am using an SD card to store log files. my question is is  does writing to the SD card frequently(small strings of <100B) vs writing large blocks (a buffer of few KBs) at once infrequently make any difference to the durability of the SD card?
 

Offline drussell

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Re: SD card wear
« Reply #1 on: September 28, 2019, 01:28:38 am »
Flash writes in blocks of typically at least 4k at a time, so if you constantly write tiny writes of say, 100 bytes, it has to write at least that whole 4k+ block each time you write.... Yes. 

Constant writes like that will reduce usable write durability.
 
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Offline JustMeHere

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Re: SD card wear
« Reply #2 on: September 28, 2019, 07:12:39 am »
Make sure you are using wear leveling.  Serial Peripheral Interface Flash File System supports this.  I'm not sure how you are accessing your flash though.

 
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Offline iMo

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Re: SD card wear
« Reply #3 on: September 28, 2019, 07:35:46 am »
All today's sdcards do the wear leveling automatically. Therefore the write latencies up to 200ms.

The endurance of the flash memory inside a mainstream 8GB sdcard could be something like 5000 writes max.

Thus your sdcard will wear out approximately in:

Time[sec] = 8GB / 4kB * 5000 / F, where F[Hz] is the frequency of your 100bytes writes.

For example writing 100bytes 1000x per second will wear out the 8GB sdcard in aprox 10.000.000 seconds.

PS: Mind the flash memory cell endurance (number of writes till it wears out) varies with the density (Gbytes on the chip) and flash technology used. It could be something between 1000 - 5000 writes. Typically the bigger the card the smaller the write endurance. Consult your sdcard's manufacturer.

« Last Edit: September 28, 2019, 07:48:31 am by imo »
Readers discretion is advised..
 
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